RFC 2446
iCalendar Transport-Independent Interoperability Protocol (iTIP) Scheduling Events, BusyTime, To-dos and Journal Entries
RFC 2446: iCalendar Transport-Independent Interoperability Protocol (iTIP) 🎀
Okay bestie, RFC 2446 is by S. Silverberg (Microsoft), S. Mansour (Netscape), F. Dawson (Lotus), and R. Hopson (ON Technologies) 💅. It came out of the Network Working Group in November 1998, and its category is Standards Track ✨, so it's a real Internet standards-track protocol and not just a vibe. The title is "iCalendar Transport-Independent Interoperability Protocol (iTIP): Scheduling Events, BusyTime, To-dos and Journal Entries" 🦋. The header doesn't list anything it obsoletes or updates, so no drama there 🌸.
Status of this Memo 📜
This doc is an Internet standards track protocol for the whole Internet community 🌈, and it's literally asking everyone to share discussion and suggestions for improvements 💬. If you want the official standardization state and status of this protocol, check the current edition of the "Internet Official Protocol Standards" (STD 1) 📚. And the best part? Distribution of this memo is unlimited 🫶.
Copyright Notice ©
Copyright (C) The Internet Society (1998). All Rights Reserved. 💜
Abstract ✨
Okay so this doc spells out how calendaring systems use iCalendar objects to interoperate with other calendar systems 📅. It does this in a general way, so there can be multiple methods of communication between systems. Subsequent documents specify interoperable methods of communications between systems that use this protocol 🧚.
The document outlines a model for calendar exchange that defines both static and dynamic event, to-do, journal and free/busy objects 🎀. Static objects transmit information from one entity to another without any expectation of continuity or referential integrity with the original item 🙈. Dynamic objects are a superset of static objects, and they'll gracefully degrade to their static counterparts for clients that only support static objects 💖. It's giving backwards compatibility, honestly 🫶.
This document specifies an Internet protocol based on the iCalendar object specification that provides scheduling interoperability between different calendar systems 🔥. The protocol is called the "iCalendar Transport-Independent Interoperability Protocol (iTIP)" 👑.
iTIP complements the iCalendar object specification by adding semantics for group scheduling methods commonly available in current calendar systems ⭐. These scheduling methods let two or more calendar systems perform transactions such as publish, schedule, reschedule, respond to scheduling requests, negotiate changes, or cancel iCalendar-based calendar components. Main character energy 💅🦋.
iTIP is defined independent of the particular transport used to transmit the scheduling information 🍓. Companion memos to iTIP provide bindings of the interoperability protocol to a number of Internet protocols 🌸.
Table of Contents 📚
1 INTRODUCTION...................................................5
1.1 FORMATTING CONVENTIONS .....................................5
1.2 RELATED DOCUMENTS ..........................................6
1.3 ITIP ROLES AND TRANSACTIONS ................................6
2 INTEROPERABILITY MODELS........................................8
2.1 APPLICATION PROTOCOL .......................................9
2.1.1 Calendar Entry State ...................................9
2.1.2 Delegation .............................................9
2.1.3 Acting on Behalf of other Calendar Users ..............10
2.1.4 Component Revisions ...................................10
2.1.5 Message Sequencing ....................................11
3 APPLICATION PROTOCOL ELEMENTS.................................12
3.1 COMMON COMPONENT RESTRICTION TABLES .......................13
3.2 METHODS FOR VEVENT CALENDAR COMPONENTS ....................14
3.2.1 PUBLISH ...............................................15
3.2.2 REQUEST ...............................................17
3.2.2.1 Rescheduling an Event..............................19
3.2.2.2 Updating or Reconfirmation of an Event.............19
3.2.2.3 Delegating an Event to another CU..................19
3.2.2.4 Changing the Organizer.............................20
3.2.2.5 Sending on Behalf of the Organizer.................20
3.2.2.6 Forwarding to An Uninvited CU......................20
3.2.2.7 Updating Attendee Status...........................21
3.2.3 REPLY .................................................21
3.2.4 ADD ...................................................23
3.2.5 CANCEL ................................................25
3.2.6 REFRESH ...............................................26
3.2.7 COUNTER ...............................................28
3.2.8 DECLINECOUNTER ........................................29
3.3 METHODS FOR VFREEBUSY COMPONENTS ..........................31
3.3.1 PUBLISH ...............................................32
3.3.2 REQUEST ...............................................33
3.3.3 REPLY .................................................34
3.4 METHODS FOR VTODO COMPONENTS ..............................35
3.4.1 PUBLISH ...............................................35
3.4.2 REQUEST ...............................................37
3.4.2.1 REQUEST for Rescheduling a VTODO...................39
3.4.2.2 REQUEST for Update or Reconfirmation of a VTODO....39
3.4.2.3 REQUEST for Delegating a VTODO.....................40
3.4.2.4 REQUEST Forwarded To An Uninvited Calendar User....40
3.4.2.5 REQUEST Updated Attendee Status....................41
3.4.3 REPLY .................................................41
3.4.4 ADD ...................................................43
3.4.5 CANCEL ................................................44
3.4.6 REFRESH ...............................................46
3.4.7 COUNTER ...............................................48
3.4.8 DECLINECOUNTER ........................................49
3.5 METHODS FOR VJOURNAL COMPONENTS ...........................50
3.5.1 PUBLISH ...............................................51
3.5.2 ADD ...................................................52
3.5.3 CANCEL ................................................53
3.6 STATUS REPLIES ............................................55
3.7 IMPLEMENTATION CONSIDERATIONS .............................57
3.7.1 Working With Recurrence Instances .....................57
3.7.2 Attendee Property Considerations ......................58
3.7.3 X-Tokens ..............................................59
4 EXAMPLES......................................................59
4.1 PUBLISHED EVENT EXAMPLES ..................................59
4.1.1 A Minimal Published Event .............................60
4.1.2 Changing A Published Event ............................60
4.1.3 Canceling A Published Event ...........................61
4.1.4 A Rich Published Event ................................62
4.1.5 Anniversaries or Events attached to entire days .......63
4.2 GROUP EVENT EXAMPLES ......................................63
4.2.1 A Group Event Request .................................64
4.2.2 Reply To A Group Event Request ........................65
4.2.3 Update An Event .......................................65
4.2.4 Countering an Event Proposal ..........................66
4.2.5 Delegating an Event ...................................68
4.2.6 Delegate Accepts the Meeting ..........................70
4.2.7 Delegate Declines the Meeting .........................71
4.2.8 Forwarding an Event Request ...........................72
4.2.9 Cancel A Group Event ..................................72
4.2.10 Removing Attendees ...................................74
4.2.11 Replacing the Organizer ..............................75
4.3 BUSY TIME EXAMPLES ........................................76
4.3.1 Request Busy Time .....................................77
4.3.2 Reply To A Busy Time Request ..........................77
4.4 RECURRING EVENT AND TIME ZONE EXAMPLES ....................78
4.4.1 A Recurring Event Spanning Time Zones .................78
4.4.2 Modify A Recurring Instance ...........................79
4.4.3 Cancel an Instance ....................................81
4.4.4 Cancel Recurring Event ................................81
4.4.5 Change All Future Instances ...........................82
4.4.6 Add A New Instance To A Recurring Event ...............82
4.4.7 Add A New Series of Instances To A Recurring Event ....83
4.4.8 Counter An Instance Of A Recurring Event ..............87
4.4.9 Error Reply To A Request ..............................88
4.5 GROUP TO-DO EXAMPLES ......................................89
4.5.1 A VTODO Request .......................................90
4.5.2 A VTODO Reply .........................................90
4.5.3 A VTODO Request for Updated Status ....................91
4.5.4 A Reply: Percent-Complete .............................91
4.5.5 A Reply: Completed ....................................92
4.5.6 An Updated VTODO Request ..............................92
4.5.7 Recurring VTODOs ......................................92
4.5.7.1 Request for a Recurring VTODO......................93
4.5.7.2 Calculating due dates in recurring VTODOs..........93
4.5.7.3 Replying to an instance of a recurring VTODO.......93
4.6 JOURNAL EXAMPLES ..........................................94
4.7 OTHER EXAMPLES ............................................94
4.7.1 Event Refresh .........................................94
4.7.2 Bad RECURRENCE-ID .....................................95
5 APPLICATION PROTOCOL FALLBACKS................................97
5.1 PARTIAL IMPLEMENTATION ....................................97
5.1.1 Event-Related Fallbacks ...............................97
5.1.2 Free/Busy-Related Fallbacks ...........................99
5.1.3 To-Do-Related Fallbacks ...............................99
5.1.4 Journal-Related Fallbacks ............................101
5.2 LATENCY ISSUES ...........................................102
5.2.1 Cancellation of an Unknown Calendar Component. .......102
5.2.2 Unexpected Reply from an Unknown Delegate ............103
5.3 SEQUENCE NUMBER ..........................................103
6 SECURITY CONSIDERATIONS......................................103
6.1 SECURITY THREATS .........................................103
6.1.1 Spoofing the "Organizer" .............................103
6.1.2 Spoofing the "Attendee" ..............................103
6.1.3 Unauthorized Replacement of the Organizer ............104
6.1.4 Eavesdropping ........................................104
6.1.5 Flooding a Calendar ..................................104
6.1.6 Procedural Alarms ....................................104
6.1.7 Unauthorized REFRESH Requests ........................104
6.2 RECOMMENDATIONS ..........................................104
6.2.1 Use of [RFC-1847] to secure iTIP transactions ........105
6.2.2 Implementation Controls ..............................105
7 ACKNOWLEDGMENTS..............................................106
8 BIBLIOGRAPHY.................................................106
9 AUTHORS' ADDRESSES...........................................107
10 FULL COPYRIGHT STATEMENT....................................1091 Introduction 🎀
okay bestie so this doc is literally about how calendaring systems use iCalendar objects to talk to other calendar systems 📅✨ like, it lays out how to schedule events, to-dos, or daily journal entries 📓, and how to search for available busy time info so you can find when people are free 🕒. it's written in a general way so systems can use multiple methods of communication 💌, and later documents spell out the transport bindings between systems 🦋 (iykyk, the details come later 💅).
this protocol is giving messages-from-an-originator-to-one-or-more-recipients 💜. for certain types of messages, a recipient may reply to update their status, and they can also send back transaction/request status info 📬. the protocol lets the originator modify or cancel the original message 🙅♀️, and recipients can suggest changes back to the originator too 🧚. and the elements of the protocol define the user roles for its transactions 👑 periodt. no cap, this is the foundation for everything else, so main character energy only 🌸
1.1. Formatting Conventions
okay so before we get into the good stuff 💅 there are some formatting conventions you need, because this doc keeps pointing at stuff from [iCAL] and [iTIP] and you have to be able to spot it instantly 👀
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY" and "OPTIONAL" in this document are to be interpreted as described in [RFC-2119]. ✨
Calendaring and scheduling roles are written in quoted strings with the first letter of each word capitalised 🎀 so "Organizer" is a role of a "Calendar User" (CU) in the scheduling protocol from [iTIP]. Calendar components from [iCAL] get the same capitalised quoted-string treatment, and they all start with the letter "V" 🦋 so "VEVENT" is the event component, "VTODO" is the to-do component and "VJOURNAL" is the daily journal component. Scheduling methods from [iTIP] are capitalised quoted strings too 💜 "REQUEST" is the method for asking for a scheduling calendar component to be created or modified, and "REPLY" is the method a recipient of a request uses to update their status with the "Organizer" of the calendar component. literally the vocab of this whole doc 😭
Properties from [iCAL] are capitalised quoted strings followed by the word "property" 🌸 so the "ATTENDEE" property is the iCalendar property used to convey the calendar address of a "Calendar User". Property parameters defined by this memo are lower case quoted strings followed by the word "parameter" 🍓 so the "value" parameter is the iCalendar property parameter used to override the default data type for a property value. Enumerated values defined by this memo are capitalised text, either alone or followed by the word "value" ⭐
In tables, the quoted-string text is written without quotes so the table stays short 🧚
1.2. Related Documents
implementers are gonna need to be familiar with a few other memos that, together with this one, describe the Internet calendaring and scheduling standards 📚 This document, [iTIP], specifies an interoperability protocol for scheduling between different implementations. The related documents are:
- [iCAL] - specifies the objects, data types, properties and property parameters used in the protocols, along with the methods for representing and encoding them;
- [iMIP] specifies an Internet email binding for [iTIP].
This memo does not attempt to repeat the specification of concepts or definitions from these other memos 🙈 Where possible, references are made to the memo that provides for the specification of these concepts or definitions. no copy-pasting, just pointing you to the right place 💅
1.3. ITIP Roles and Transactions
ITIP defines methods for exchanging [iCAL] objects for the purposes of group calendaring and scheduling between "Calendar Users" (CUs) 🗓️ CUs take on one of two roles in iTIP. The CU who initiates an exchange takes on the role of "Organizer". For example, the CU who proposes a group meeting is the "Organizer". The CUs asked to participate in the group meeting by the "Organizer" take on the role of "Attendee". Note that "role" is also a descriptive parameter to the _ATTENDEE_ property 🥹 Its use is to convey descriptive context to an "Attendee" such as "chair", "req-participant" or "non-participant" and has nothing to do with the calendaring workflow. so "role" means two different things, don't mix them up 💀
The ITIP methods are listed below and their usage and semantics are defined in section 3 of this document. here's the full lineup 👑
+================+==================================================+
| Method | Description |
|================+==================================================|
| PUBLISH | Used to publish a calendar entry to one or more |
| | Calendar Users. There is no interactivity |
| | between the publisher and any other calendar |
| | user. An example might include a baseball team |
| | publishing its schedule to the public. |
| | |
| REQUEST | Used to schedule a calendar entry with other |
| | Calendar Users. Requests are interactive in that |
| | they require the receiver to respond using |
| | the Reply methods. Meeting Requests, Busy |
| | Time requests and the assignment of VTODOs to |
| | other Calendar Users are all examples. |
| | Requests are also used by the "Organizer" to |
| | update the status of a calendar entry. |
| | |
| REPLY | A Reply is used in response to a Request to |
| | convey "Attendee" status to the "Organizer". |
| | Replies are commonly used to respond to meeting |
| | and task requests. |
| | |
| ADD | Add one or more instances to an existing |
| | VEVENT, VTODO, or VJOURNAL. |
| | |
| CANCEL | Cancel one or more instances of an existing |
| | VEVENT, VTODO, or VJOURNAL. |
| | |
| REFRESH | The Refresh method is used by an "Attendee" to |
| | request the latest version of a calendar entry. |
| | |
| COUNTER | The Counter method is used by an "Attendee" to |
| | negotiate a change in the calendar entry. |
| | Examples include the request to change a |
| | proposed Event time or change the due date for a |
| | VTODO. |
| | |
| DECLINE- | Used by the "Organizer" to decline the proposed |
| COUNTER | counter-proprosal. |
+================+==================================================+Group scheduling in iTIP is accomplished using the set of "request" and "response" methods described above. The following table shows the methods broken down by who can send them 📋
+================+==================================================+
| Originator | Methods |
|================+==================================================|
| Organizer | PUBLISH, REQUEST, ADD, CANCEL, DECLINECOUNTER |
| | |
| Attendee | REPLY, REFRESH, COUNTER |
| | REQUEST only when delegating |
+================+==================================================+Note that for some calendar component types, the allowable methods are a subset of the above set. 👀 so not every component gets every method, check before you assume ✨
2. Interoperability Models
there are two distinct protocols relevant to interoperability 🫶 an "Application Protocol" and a "Transport Protocol". The Application Protocol defines the content of the iCalendar objects sent between sender and receiver to accomplish the scheduling transactions listed above. The Transport Protocol defines how the iCalendar objects are sent between the sender and receiver. This document focuses on the Application Protocol. Binding documents such as [iMIP] focus on the Transport Protocol. so the app protocol is the what, the transport is the how 🚚
The connection between Sender and Receiver in the diagram below refers to the Application Protocol. The iCalendar objects passed from the Sender to the Receiver are presented in Section 3, Application Protocol Elements. 🦋
+----------+ +----------+
| | iTIP | |
| Sender |<-------------------->| Receiver |
| | | |
+----------+ +----------+There are several variations of this diagram in which the Sender and Receiver take on various roles of a "Calendar User Agent" (CUA) or a "Calendar Service" (CS). 🌈
The architecture of iTIP is depicted in the diagram below. An application written to this specification may work with bindings for the store-and-forward transport, the real time transport, or both. Also note that iTIP could be bound to other transports. 🧚
+------------------------------------------+
| iTIP |
+------------------------------------------+
|Real-time | Store-and-Fwd | Other |
|Transport | Transport | Transports... |
+------------------------------------------+2.1. Application Protocol
In the iTIP model, a calendar entry is created and managed by an "Organizer". The "Organizer" interacts with other CUs by sending one or more of the iTIP messages listed above. "Attendees" use the "REPLY" method to communicate their status. "Attendees" do not make direct changes to the master calendar entry. They can, however, use the "COUNTER" method to suggest changes to the "Organizer". In any case, the "Organizer" has complete control over the master calendar entry. 👑 attendees can suggest, the organizer is the one who decides, no drama 💅
2.1.1. Calendar Entry State
There are two distinct states relevant to calendar entries: the overall state of the entry and the state associated with an "Attendee" to that entry. 🌸
The state of an entry is defined by the "STATUS" property and is controlled by the "Organizer." There is no default value for the "STATUS" property. The "Organizer" sets the "STATUS" property to the appropriate value for each calendar entry. ⭐
The state of a particular "Attendee" relative to an entry is defined by the "partstat" parameter in the "ATTENDEE" property for each "Attendee". When an "Organizer" issues the initial entry, "Attendee" status is unknown. The "Organizer" specifies this by setting the "partstat" parameter to "NEEDS-ACTION". Each "Attendee" modifies their "ATTENDEE" property "partstat" parameter to an appropriate value as part of a "REPLY" message sent back to the "Organizer". the whole status dance in one paragraph 🥹🎀
2.1.2. Delegation
Delegation is defined as the process by which an "Attendee" grants another CU (or several CUs) the right to attend on their behalf. The "Organizer" is made aware of this change because the delegating "Attendee" informs the "Organizer". These steps are detailed in the REQUEST method section. 🫣 the full delegation steps live in the REQUEST section, so go find them when we get there 💖
2.1.3 Acting on Behalf of other Calendar Users ✨
okay so in lots of orgs, one person ends up acting on behalf of someone else to set up or reply to meeting requests 💁♀️ and ITIP has two ways to make that work 🎀
first up, the "Organizer" gets its own special spot, separate from the "Attendees" 👑 every response from an "Attendee" flows back to the "Organizer", so it's super easy to tell apart the calendar user who's running the meeting from the people just showing up. iCalendar also gives each "Attendee" a descriptive role. so one or more "Attendees" can be the "chair" 🪑 and the "chair" and the "Organizer" might be the same person, or might not be! this is literally perfect for when an assistant handles the logistics for a boss who chairs the meeting. iykyk 💅
second, you can put a "sent-by" parameter on either the "Organizer" or "Attendee" property 🦋 when it's there, it tells everyone that the responding CU was acting for the "Attendee" or "Organizer" it names. pretty iconic, ngl 🫶
2.1.4 Component Revisions 🔥
the "SEQUENCE" property is how the "Organizer" says "hey, this component has been revised" 🌸 the actual rules for bumping "SEQUENCE" live in [iCAL]. but bestie, I'm going to paraphrase them here, just so you can see how they play out in [iTIP]. for a given "UID" in a calendar component:
- for the "PUBLISH" and "REQUEST" methods, the "SEQUENCE" property value gets incremented according to the rules in [iCAL] 📈
- the "SEQUENCE" property value MUST be incremented every time the "Organizer" uses the "ADD" or "CANCEL" methods 💀
- the "SEQUENCE" property value MUST NOT be incremented when using "REPLY", "REFRESH", "COUNTER", "DECLINECOUNTER", or when sending a delegation "REQUEST" 🙈
sometimes the "Organizer" never gets replies to the final revision 😭 in that case, it can send an update "REQUEST" with RSVP=TRUE set for all "Attendees", so the current responses can be collected. main character move 👑
also, the "SEQUENCE" value in an "Attendee's" response might not always match the "Organizer's" latest revision 🤷♀️ implementations are allowed to have the CUA tell the CU that the response is for an entry that's been revised, and then let the CU decide whether to accept it. your call, queen 💖
2.1.5 Message Sequencing 🧚
so CUAs that handle the [iTIP] application protocol have to match up components in a calendar store with components that arrive in [iTIP] messages all the time 📅 like, an event might get updated with a newer version of itself, and the CUA has to correlate the version already in the store with the version in the [iTIP] message. but wait, it gets messier 😵💫 for a bunch of reasons, [iTIP] messages can show up out of order. an "Organizer" could get a reply to an OLD revision AFTER it already got a reply to a newer one. chaotic, I know 💀
so to keep things interoperable and handle messages that arrive out of order, follow these rules:
- the primary key for referencing a particular iCalendar component is the "UID" property value. to reference an instance of a recurring component, the primary key is made from the "UID" and the "RECURRENCE-ID" properties 🔑
- the secondary key for referencing a component is the "SEQUENCE" property value. for components with the same "UID", the one with the highest numeric "SEQUENCE" value obsoletes all the other revisions with lower values 📈
- "Attendees" send "REPLY" messages to the "Organizer". for replies with the same "UID" property value, the "SEQUENCE" value says which revision of the component the "Attendee" is replying to. the reply with the highest numeric "SEQUENCE" value obsoletes all the other replies with lower values 💌
- if the "UID" and "SEQUENCE" properties both match, the "DTSTAMP" property is the tie-breaker. the component with the latest "DTSTAMP" overrides everything else. same deal for "Attendee" responses: if the "UID" and "SEQUENCE" values match, the response with the latest "DTSTAMP" wins ⏰
so yeah, CUAs must persist the following component properties: "UID", "RECURRENCE-ID", "SEQUENCE", and "DTSTAMP". and for each "ATTENDEE" property of a component, CUAs must also persist the "SEQUENCE" and "DTSTAMP" values tied to that "Attendee's" response 🗂️✨
3 Application Protocol Elements 🦋
ITIP messages are "text/calendar" MIME entities that carry calendaring and scheduling info 📨 the specific type of [iCAL] message is called the "method type". each method type is identified by a "METHOD" property that's part of the "text/calendar" content type. the table below shows which combos of calendar components and method types this memo supports 🌈
+=================================================+
| | VEVENT | VTODO | VJOURNAL | VFREEBUSY |
|=================================================|
|Publish | Yes | Yes | Yes | Yes |
|Request | Yes | Yes | No | Yes |
|Refresh | Yes | Yes | No | No |
|Cancel | Yes | Yes | Yes | No |
|Add | Yes | Yes | Yes | No |
|Reply | Yes | Yes | No | Yes |
|Counter | Yes | Yes | No | No |
|Decline- | | | | |
|Counter | Yes | Yes | No | No |
+=================================================+each method type is defined by its associated components and properties 💅 some are required, some are optional, and some are excluded. the restrictions are written here using a simple "restriction table". the first column names a component or property. properties of the iCalendar object aren't indented, but properties of a component are 🫶 the second column has "MUST" if the component or property must be present, "MAY" if it's optional, and "NOT" if it must not be present. entries in that second column sometimes come with comments to clarify things ✨
3.1 Common Component Restriction Tables 💖
this restriction table covers properties of the iCalendar object, meaning the properties at the outermost scope 🎀 the presence column uses these values to say whether a property is required, whether it's optional, and how many times it can show up in the iCalendar object:
Presence Value Description
--------------------------------------------------------------
1 One instance MUST be present
1+ At least one instance MUST be present
0 Instances of this property Must NOT be present
0+ Multiple instances MAY be present
0 or 1 Up to 1 instance of this property MAY be present
---------------------------------------------------------------the tables also call out "X-PROPERTY" and "X-COMPONENT" to show where vendor-specific properties and components can appear 🌸 the tables don't lay out the restrictions on property parameters, though. those are defined in [iCAL] 📚
Component/Property Presence
------------------- ----------------------------------------------
CALSCALE 0 or 1
PRODID 1
VERSION 1 Value MUST be "2.0"
X-PROPERTY 0+DateTime values MAY refer to a "VTIMEZONE" component. the property restrictions in the table below apply to any "VTIMEZONE" component in an ITIP message 🌍
Component/Property Presence
------------------- ----------------------------------------------
VTIMEZONE 0+ MUST be present if any date/time refers
to timezone
DAYLIGHT 0+ MUST be one or more of either STANDARD or
DAYLIGHT
COMMENT 0 or 1
DTSTART 1 MUST be local time format
RDATE 0+ if present RRULE MUST NOT be present
RRULE 0+ if present RDATE MUST NOT be present
TZNAME 0 or 1
TZOFFSET 1
TZOFFSETFROM 1
TZOFFSETTO 1
X-PROPERTY 0+
LAST-MODIFIED 0 or 1
STANDARD 0+ MUST be one or more of either STANDARD or
DAYLIGHT
COMMENT 0 or 1
DTSTART 1 MUST be local time format
RDATE 0+ if present RRULE MUST NOT be present
RRULE 0+ if present RDATE MUST NOT be present
TZNAME 0 or 1
TZOFFSETFROM 1
TZOFFSETTO 1
X-PROPERTY 0+
TZID 1
TZURL 0 or 1
X-PROPERTY 0+the property restrictions in the table below apply to any "VALARM" component in an ITIP message ⏰
Component/Property Presence
------------------- ----------------------------------------------
VALARM 0+
ACTION 1
ATTACH 0+
DESCRIPTION 0 or 1
DURATION 0 or 1 if present REPEAT MUST be present
REPEAT 0 or 1 if present DURATION MUST be present
SUMMARY 0 or 1
TRIGGER 1
X-PROPERTY 0+3.2 Methods for VEVENT Calendar Components ✨
Okay bestie, this section is all about the VEVENT calendar component, aka the actual event 🎀 Every method gets its own table that spells out exactly which properties are allowed, so there's no guessing. Here's the lineup 💅
+================+==================================================+
| Method | Description |
|================+==================================================|
| PUBLISH | Post notification of an event. Used primarily as |
| | a method of advertising the existence of an |
| | event. |
| | |
| REQUEST | Make a request for an event. This is an explicit |
| | invitation to one or more "Attendees". Event |
| | Requests are also used to update or change an |
| | existing event. Clients that cannot handle |
| | REQUEST may degrade the event to view it as an |
| | PUBLISH. |
| | |
| REPLY | Reply to an event request. Clients may set their |
| | status ("partstat") to ACCEPTED, DECLINED, |
| | TENTATIVE, or DELEGATED. |
| | |
| ADD | Add one or more instances to an existing event. |
| | |
| CANCEL | Cancel one or more instances of an existing |
| | event. |
| | |
| REFRESH | A request is sent to an "Organizer" by an |
| | "Attendee" asking for the latest version of an |
| | event to be resent to the requester. |
| | |
| COUNTER | Counter a REQUEST with an alternative proposal, |
| | Sent by an "Attendee" to the "Organizer". |
| | |
| DECLINECOUNTER | Decline a counter proposal. Sent to an |
| | "Attendee" by the "Organizer". |
+================+==================================================+3.2.1 PUBLISH 📣
PUBLISH is an unsolicited posting of an iCalendar object, so it just drops in without anyone asking 💅 Any CU may add published components to their calendar 🦋 The "Organizer" MUST be present in a published iCalendar component, and "Attendees" MUST NOT be present 🙅♀️ That's the whole vibe. Its expected usage is encapsulating an arbitrary event as an iCalendar object. After that, the "Organizer" may update it (with another "PUBLISH" method), add instances to it (with an "ADD" method), or cancel it (with a "CANCEL" method) 🔁
A PUBLISH object has to be an iCalendar object that conforms to these property constraints 📋
Component/Property Presence
------------------- ----------------------------------------------
METHOD 1 MUST equal "PUBLISH"
VEVENT 1+
DTSTAMP 1
DTSTART 1
ORGANIZER 1
SUMMARY 1 Can be null.
UID 1
RECURRENCE-ID 0 or 1 only if referring to an instance of a
recurring calendar component. Otherwise
it MUST NOT be present.
SEQUENCE 0 or 1 MUST be present if value is greater than
0, MAY be present if 0
ATTACH 0+
CATEGORIES 0 or 1 This property may contain a list of
values
CLASS 0 or 1
COMMENT 0 or 1
CONTACT 0+
CREATED 0 or 1
DESCRIPTION 0 or 1 Can be null
DTEND 0 or 1 if present DURATION MUST NOT be present
DURATION 0 or 1 if present DTEND MUST NOT be present
EXDATE 0+
EXRULE 0+
GEO 0 or 1
LAST-MODIFIED 0 or 1
LOCATION 0 or 1
PRIORITY 0 or 1
RDATE 0+
RELATED-TO 0+
RESOURCES 0 or 1 This property MAY contain a list of values
RRULE 0+
STATUS 0 or 1 MAY be one of TENTATIVE/CONFIRMED/CANCELLED
TRANSP 0 or 1
URL 0 or 1
X-PROPERTY 0+
ATTENDEE 0
REQUEST-STATUS 0
VALARM 0+
VFREEBUSY 0
VJOURNAL 0
VTODO 0
VTIMEZONE 0+ MUST be present if any date/time refers to
a timezone
X-COMPONENT 0+3.2.2 REQUEST 🤹♀️
The REQUEST method in a VEVENT component is a multitasker 💜 It can:
- Invite "Attendees" to an event;
- Reschedule an existing event;
- Response to a REFRESH request;
- Update the details of an existing event, without rescheduling it;
- Update the status of "Attendees" of an existing event, without rescheduling it;
- Reconfirm an existing event, without rescheduling it;
- Forward a "VEVENT" to another uninvited CU.
- For an existing "VEVENT" calendar component, delegate the role of "Attendee" to another CU;
- For an existing "VEVENT" calendar component, changing the role of "Organizer" to another CU.
The "Organizer" is the one who originates the REQUEST 📨 The recipients are the CUs invited to the event, aka the "Attendees". Then "Attendees" use the REPLY method to convey their attendance status back to the "Organizer" 💌
The UID and SEQUENCE properties are how you tell the different REQUEST vibes apart 🕵️ If the UID property value in the REQUEST isn't found on the recipient's calendar, then the REQUEST is for a brand new VEVENT calendar component. If the UID value is already on the calendar, then the REQUEST is for a rescheduling, an update, or a reconfirm of that VEVENT 🔍
For the REQUEST method, multiple VEVENT components in a single iCalendar object are only permitted when they share the same UID property. Like, a series of recurring events can have instance-specific info, and in that case you need multiple VEVENT components to express the entire series 🔁
This method type is an iCalendar object that conforms to these property constraints 📋
Component/Property Presence
-----------------------------------------------------------------
METHOD 1 MUST be "REQUEST"
VEVENT 1+ All components MUST have the same UID
ATTENDEE 1+
DTSTAMP 1
DTSTART 1
ORGANIZER 1
SEQUENCE 0 or 1 MUST be present if value is greater than 0,
MAY be present if 0
SUMMARY 1 Can be null
UID 1
ATTACH 0+
CATEGORIES 0 or 1 This property may contain a list of values
CLASS 0 or 1
COMMENT 0 or 1
CONTACT 0+
CREATED 0 or 1
DESCRIPTION 0 or 1 Can be null
DTEND 0 or 1 if present DURATION MUST NOT be present
DURATION 0 or 1 if present DTEND MUST NOT be present
EXDATE 0+
EXRULE 0+
GEO 0 or 1
LAST-MODIFIED 0 or 1
LOCATION 0 or 1
PRIORITY 0 or 1
RDATE 0+
RECURRENCE-ID 0 or 1 only if referring to an instance of a
recurring calendar component. Otherwise it
MUST NOT be present.
RELATED-TO 0+
REQUEST-STATUS 0+
RESOURCES 0 or 1 This property MAY contain a list of values
RRULE 0+
STATUS 0 or 1 MAY be one of TENTATIVE/CONFIRMED
TRANSP 0 or 1
URL 0 or 1
X-PROPERTY 0+
VALARM 0+
VTIMEZONE 0+ MUST be present if any date/time refers to
a timezone
X-COMPONENT 0+
VFREEBUSY 0
VJOURNAL 0
VTODO 03.2.2.1 Rescheduling an Event 📆
The REQUEST method may be used to reschedule an event. A rescheduled event involves a change to the existing event in terms of its time or recurrence intervals, and possibly the location or description. If the recipient CUA of a REQUEST method finds that the UID property value already exists on the calendar, but the SEQUENCE (or DTSTAMP) property value in the REQUEST method is greater than the value for the existing event, then the REQUEST method describes a rescheduling of the event ⏰
3.2.2.2 Updating or Reconfirmation of an Event 🫶
The REQUEST method may be used to update or reconfirm an event. An update to an existing event doesn't involve changes to the time or recurrence intervals, and might not involve a change to the location or description for the event. If the recipient CUA of a REQUEST method finds that the UID property value already exists on the calendar, and the SEQUENCE property value in the REQUEST is the same as the value for the existing event, then the REQUEST method describes an update of the event details, but no rescheduling of the event 🌸
The update REQUEST method is the appropriate response to a REFRESH method sent from an "Attendee" to the "Organizer" of an event 🔄
The "Organizer" of an event may also send unsolicited REQUEST methods. Those unsolicited REQUEST methods may be used to update the details of the event without rescheduling it, to update the "partstat" parameter of "Attendees", or to reconfirm the event 💅✨
3.2.2.3 Delegating an Event to another CU ✨
okay so some calendar systems let "Attendees" pass their spot at an event to another calendar user. that's delegating 💅 ITIP handles it with the workflow below. any "Attendee" can delegate their right to join a calendar VEVENT to another CU. the delegate shows up instead of the original "Attendee", NOT in addition to them 🙈 the delegator MUST notify the "Organizer" about it using the steps below. implementations may support or restrict delegation as they see fit 🧚 for example, some might stop a delegate from passing a "REQUEST" on to another CU.
the "Delegator" forwards the existing "REQUEST" to the "Delegate" 📨 the "REQUEST" method MUST include an ATTENDEE property with the calendar address of the "Delegate". the "Delegator" MUST also send a "REPLY" method to the "Organizer" with the "Delegator's" ATTENDEE property partstat parameter value set to delegated. and the delegated-to parameter MUST be included with the calendar address of the "Delegate" 🎀
when the request comes in, the "Delegate" MUST send a "REPLY" method to the "Organizer" and optionally, to the "Delegator" 🦋 the "REPLY" method SHOULD include the ATTENDEE property with the delegated-from parameter value set to the "Delegator's" calendar address.
the "Delegator" may keep getting updates to the event even though they won't be attending 👀 they do this by setting their role attribute to NON-PARTICIPANT in the "REPLY" to the "Organizer". main character behavior, fr 💜
3.2.2.4 Changing the Organizer 👑
so this is the situation where the "Organizer" of a VEVENT can't do the job anymore and just bails without handing the role to anyone 😭 when that happens, the "Attendees" of the VEVENT can use out-of-band mechanisms to talk it through and agree on a new "Organizer" 🫶 the new "Organizer" should then send out a new "REQUEST" with a modified version of the VEVENT, where the SEQUENCE number has been incremented and the ORGANIZER property now holds the calendar address of the new "Organizer". it's giving clean handoff ✨
3.2.2.5 Sending on Behalf of the Organizer 🌸
there are a bunch of scenarios where a calendar user has to act on behalf of the "Organizer" without anyone formally changing roles 💅 like, the CU designated as "Organizer" might be sick or unable to do the organizer stuff 🤒 in these cases iTIP supports one CU acting on behalf of another. using the sent-by parameter, a calendar user could send an updated VEVENT REQUEST. when one CU sends on behalf of another CU, the "Attendee" responses still go back to the CU designated as "Organizer" 📬 so the replies don't get lost, bestie 🫶
3.2.2.6 Forwarding to An Uninvited CU 🦋
an invited "Attendee" can bring in another uninvited CU to the event 🙌 they do it by forwarding the original "REQUEST" method to that uninvited CU. the "Organizer" gets to decide whether the uninvited CU joins the attendee list 👑 if the "Organizer" says no, nothing else is needed, but the "Organizer" MAY send the uninvited CU a CANCEL message 💀 if the "Organizer" says yes, a new ATTENDEE property gets added for the uninvited CU, with its property parameters set however the "Organizer" thinks is right ✨ when forwarding a "REQUEST" to another CU, the forwarding "Attendee" MUST NOT make changes to the VEVENT property set. hands off the VEVENT, no edits, periodt 🤚
3.2.2.7 Updating Attendee Status 🔥
the "Organizer" of an event can also ask one or more "Attendees" for an updated status 📋 the "Organizer" sends a "REQUEST" method to the "Attendee" and sets the ATTENDEE;RSVP=TRUE property parameter. the SEQUENCE property for the event stays the same as its previous value. the recipient will see that the only change in the "REQUEST" is their RSVP property parameter asking for an updated status 🧠 the recipient SHOULD respond with a "REPLY" method showing their current status with respect to the "REQUEST" 💖
3.2.3 REPLY 💌
the "REPLY" method in a VEVENT calendar component is how you respond (accept or decline, for example) to a "REQUEST" or reply to a delegation "REQUEST" ✨ when it's a delegation response, the "Delegator" SHOULD include the calendar address of the "Delegate" in the delegated-to property parameter of the "Delegator's" ATTENDEE property. and the "Delegate" SHOULD include the calendar address of the "Delegator" in the delegated-from property parameter of the "Delegate's" ATTENDEE property 🎀
the "REPLY" method may also be used to respond to an unsuccessful "REQUEST" method 🙃 depending on the REQUEST-STATUS property value, no scheduling action might have happened at all.
the "Organizer" of an event can get a "REPLY" from a CU that wasn't in the original "REQUEST" 👀 for example, a "REPLY" may come from a "Delegate" 🧚 plus the "REPLY" method may also show up from an unknown CU (a "Party Crasher" 🙈). that uninvited "Attendee" may be accepted, or the "Organizer" may cancel the event for them by sending a "CANCEL" method to the uninvited "Attendee". plot twist, lmao 💀
an "Attendee" can add a message for the "Organizer" using the COMMENT property 💬 like, if someone says they're tentatively in and wants the "Organizer" to know why, that reason goes in the COMMENT property value 🫶
the "Organizer" may also get a "REPLY" from one CU on behalf of another 🌈 just like the scenario above for the "Organizer", "Attendees" may have another CU respond for them. this is done with the sent-by parameter ✨
the optional properties in the table below (the ones marked "0+" or "0 or 1") MUST NOT be changed from the original request 🚫 if property changes are wanted, the COUNTER message must be used.
this method type is an iCalendar object that follows these property constraints 📜
Component/Property Presence
------------------- ----------------------------------------------
METHOD 1 MUST be "REPLY"
VEVENT 1+ All components MUST have the same UID
ATTENDEE 1 MUST be the address of the Attendee
replying.
DTSTAMP 1
ORGANIZER 1
RECURRENCE-ID 0 or 1 only if referring to an instance of a
recurring calendar component. Otherwise
it must NOT be present.
UID 1 MUST be the UID of the original REQUEST
SEQUENCE 0 or 1 MUST if non-zero, MUST be the sequence
number of the original REQUEST. MAY be
present if 0.
ATTACH 0+
CATEGORIES 0 or 1 This property may contain a list of values
CLASS 0 or 1
COMMENT 0 or 1
CONTACT 0+
CREATED 0 or 1
DESCRIPTION 0 or 1
DTEND 0 or 1 if present DURATION MUST NOT be present
DTSTART 0 or 1
DURATION 0 or 1 if present DTEND MUST NOT be present
EXDATE 0+
EXRULE 0+
GEO 0 or 1
LAST-MODIFIED 0 or 1
LOCATION 0 or 1
PRIORITY 0 or 1
RDATE 0+
RELATED-TO 0+
RESOURCES 0 or 1 This property MAY contain a list of values
REQUEST-STATUS 0+
RRULE 0+
STATUS 0 or 1
SUMMARY 0 or 1
TRANSP 0 or 1
URL 0 or 1
X-PROPERTY 0+
VTIMEZONE 0 or 1 MUST be present if any date/time refers
to a timezone
X-COMPONENT 0+
VALARM 0
VFREEBUSY 0
VJOURNAL 0
VTODO 03.2.4 ADD ➕
the "ADD" method in a VEVENT calendar component adds one or more instances to an existing "VEVENT" 🌟 unlike the "REQUEST" method, when issuing an "ADD" method, the "Organizer" does NOT send the full "VEVENT" description, just the new instance(s) 🙌 "ADD" is super useful when there are instance-specific properties you want to keep in a recurring "VEVENT". for example, an "Organizer" might have set up a weekly Thursday meeting 🍓 then a few instances changed. the location or start time might have shifted, or some instances might have their own unique DESCRIPTION properties 🤯 the "ADD" method lets the "Organizer" add new instances to an existing event in one single ITIP message, without redefining the whole recurring pattern. efficient and iconic 💅
the UID must be the one from the existing event. if the UID property value in the "ADD" can't be found on the recipient's calendar, the recipient SHOULD send a "REFRESH" to the "Organizer" so they can get the latest version of the "VEVENT" 🔄 if an "Attendee" implementation doesn't support the "ADD" method, it should respond with a REQUEST-STATUS value of 3.14 and ask for a "REFRESH" 🥺
this method type is an iCalendar object that follows these property constraints 📜
Component/Property Presence
------------------- ----------------------------------------------
METHOD 1 MUST be "ADD"
VEVENT 1
DTSTAMP 1
DTSTART 1
ORGANIZER 1
SEQUENCE 1 MUST be greater than 0
SUMMARY 1 Can be null
UID 1 MUST match that of the original event
ATTACH 0+
ATTENDEE 0+
CATEGORIES 0 or 1 This property MAY contain a list of values
CLASS 0 or 1
COMMENT 0 or 1
CONTACT 0+
CREATED 0 or 1
DESCRIPTION 0 or 1 Can be null
DTEND 0 or 1 if present DURATION MUST NOT be present
DURATION 0 or 1 if present DTEND MUST NOT be present
EXDATE 0+
EXRULE 0+
GEO 0 or 1
LAST-MODIFIED 0 or 1
LOCATION 0 or 1
PRIORITY 0 or 1
RDATE 0+
RELATED-TO 0+
RESOURCES 0 or 1 This property MAY contain a list of values
RRULE 0+
STATUS 0 or 1 MAY be one of TENTATIVE/CONFIRMED
TRANSP 0 or 1
URL 0 or 1
X-PROPERTY 0+
RECURRENCE-ID 0
REQUEST-STATUS 0
VALARM 0+
VTIMEZONE 0+ MUST be present if any date/time refers to
a timezone
X-COMPONENT 0+
VFREEBUSY 0
VTODO 0
VJOURNAL 03.2.5 CANCEL 🚫💅
okay so the "CANCEL" method in a "VEVENT" calendar component is how the "Organizer" sends a cancellation notice for an existing event request to the "Attendees". 🫶 For a recurring event, you can cancel the whole thing or just some of the instances. To cancel the complete range of a recurring event, the "UID" property value for the event MUST be specified and a "RECURRENCE-ID" MUST NOT be specified in the "CANCEL" method. If you want to cancel one individual instance instead, the "RECURRENCE-ID" property value for the event MUST be specified in the "CANCEL" method. 🦋
there are two options for canceling a sequence of instances of a recurring "VEVENT" calendar component:
- (a) the
"RECURRENCE-ID"property for an instance in the sequence MUST be specified with the"RANGE"property parameter value of THISANDPRIOR (or THISANDFUTURE) to indicate cancellation of the specified"VEVENT"calendar component and all instances before (or after); or - (b) individual recurrence instances may be cancelled by specifying multiple
"RECURRENCE-ID"properties corresponding to the instances to be cancelled.
when a "VEVENT" gets cancelled, the "SEQUENCE" property value MUST be incremented. 🔢✨
this method type is an iCalendar object that conforms to the following property constraints: 🌸
Component/Property Presence
------------------- ----------------------------------------------
METHOD 1 MUST be "CANCEL"
VEVENT 1+ All must have the same UID
ATTENDEE 0+ MUST include all "Attendees" being removed
the event. MUST include all "Attendees" if
the entire event is cancelled.
DTSTAMP 1
ORGANIZER 1
SEQUENCE 1
UID 1 MUST be the UID of the original REQUEST
COMMENT 0 or 1
ATTACH 0+
CATEGORIES 0 or 1 This property may contain a list of values
CLASS 0 or 1
CONTACT 0+
CREATED 0 or 1
DESCRIPTION 0 or 1
DTEND 0 or 1 if present DURATION MUST NOT be present
DTSTART 0 or 1
DURATION 0 or 1 if present DTEND MUST NOT be present
EXDATE 0+
EXRULE 0+
GEO 0 or 1
LAST-MODIFIED 0 or 1
LOCATION 0 or 1
PRIORITY 0 or 1
RDATE 0+
RECURRENCE-ID 0 or 1 MUST be present if referring to one or
more or more recurring instances.
Otherwise it MUST NOT be present
RELATED-TO 0+
RESOURCES 0 or 1
RRULE 0+
STATUS 0 or 1 MUST be set to CANCELLED. If uninviting
specific "Attendees" then MUST NOT be
included.
SUMMARY 0 or 1
TRANSP 0 or 1
URL 0 or 1
X-PROPERTY 0+
REQUEST-STATUS 0
VTIMEZONE 0+ MUST be present if any date/time refers to
a timezone
X-COMPONENT 0+
VTODO 0
VJOURNAL 0
VFREEBUSY 0
VALARM 03.2.6 REFRESH 🔄🎀
the "REFRESH" method in a "VEVENT" calendar component is how "Attendees" of an existing event ask the event "Organizer" for an updated description. 💖 The "REFRESH" method must specify the "UID" property of the event to update. If you want a single recurrence instance, you can specify the "RECURRENCE-ID" property that goes with the associated event. The "Organizer" replies with the latest description and version of the event. 🧚
this method type is an iCalendar object that conforms to the following property constraints: 🍓
Component/Property Presence
------------------- ----------------------------------------------
METHOD 1 MUST be "REFRESH"
VEVENT 1
ATTENDEE 1 MUST be the address of requestor
DTSTAMP 1
ORGANIZER 1
UID 1 MUST be the UID associated with original
REQUEST
COMMENT 0 or 1
RECURRENCE-ID 0 or 1 MUST only if referring to an instance of a
recurring calendar component. Otherwise
it must NOT be present.
X-PROPERTY 0+
ATTACH 0
CATEGORIES 0
CLASS 0
CONTACT 0
CREATED 0
DESCRIPTION 0
DTEND 0
DTSTART 0
DURATION 0
EXDATE 0
EXRULE 0
GEO 0
LAST-MODIFIED 0
LOCATION 0
PRIORITY 0
RDATE 0
RELATED-TO 0
REQUEST-STATUS 0
RESOURCES 0
RRULE 0
SEQUENCE 0
STATUS 0
SUMMARY 0
TRANSP 0
URL 0
X-COMPONENT 0+
VTODO 0
VJOURNAL 0
VFREEBUSY 0
VTIMEZONE 0
VALARM 03.2.7 COUNTER 🙋♀️💜
the "COUNTER" method for a "VEVENT" calendar component is how an "Attendee" of an existing event sends the "Organizer" a counter proposal to the event description. 👑 The "Attendee" sends this message to the "Organizer" of the event. 💅
the counter proposal is an iCalendar object made up of a VEVENT calendar component that describes the complete description of the alternate event. 🌈
the "Organizer" can reject the counter proposal by sending the "Attendee" a VEVENT "DECLINECOUNTER" method. Or the "Organizer" can accept it by rescheduling the event as described in section 3.2.2.1 Rescheduling an Event. ✨
this method type is an iCalendar object that conforms to the following property constraints: 🌸
Component/Property Presence
------------------- ----------------------------------------------
METHOD 1 MUST be "COUNTER"
VEVENT 1
DTSTAMP 1
DTSTART 1
ORGANIZER 1 MUST be the "Organizer" of the original
event
SEQUENCE 1 MUST be present if value is greater than 0,
MAY be present if 0
SUMMARY 1 Can be null
UID 1 MUST be the UID associated with the REQUEST
being countered
ATTACH 0+
ATTENDEE 0+ Can also be used to propose other
"Attendees"
CATEGORIES 0 or 1 This property may contain a list of values
CLASS 0 or 1
COMMENT 0 or 1
CONTACT 0+
CREATED 0 or 1
DESCRIPTION 0 or 1
DTEND 0 or 1 if present DURATION MUST NOT be present
DURATION 0 or 1 if present DTEND MUST NOT be present
EXDATE 0+
EXRULE 0+
GEO 0 or 1
LAST-MODIFIED 0 or 1
LOCATION 0 or 1
PRIORITY 0 or 1
RDATE 0+
RECURRENCE-ID 0 or 1 MUST only if referring to an instance of a
recurring calendar component. Otherwise it
MUST NOT be present.
RELATED-TO 0+
REQUEST-STATUS 0+
RESOURCES 0 or 1 This property may contain a list of values
RRULE 0+
STATUS 0 or 1 Value must be one of CONFIRMED/TENATIVE/
CANCELLED
TRANSP 0 or 1
URL 0 or 1
X-PROPERTY 0+
VALARM 0+
VTIMEZONE 0+ MUST be present if any date/time refers to
a timezone
X-COMPONENT 0+
VTODO 0
VJOURNAL 0
VFREEBUSY 03.2.8 DECLINECOUNTER 🙅♀️🦋
the "DECLINECOUNTER" method in a "VEVENT" calendar component is how the "Organizer" of an event rejects a counter proposal submitted by an "Attendee". 💀 The "Organizer" must send the "DECLINECOUNTER" message to the "Attendee" that sent the "COUNTER" method to the "Organizer". 🥺
this method type is an iCalendar object that conforms to the following property constraints: 🫶
Component/Property Presence
------------------- ----------------------------------------------
METHOD 1 MUST be "DECLINECOUNTER"
VEVENT 1
DTSTAMP 1
ORGANIZER 1
UID 1 MUST, same UID specified in original
REQUEST and subsequent COUNTER
COMMENT 0 or 1
RECURRENCE-ID 0 or 1 MUST only if referring to an instance of a
recurring calendar component. Otherwise it
MUST NOT be present.
REQUEST-STATUS 0+
SEQUENCE 0 OR 1 MUST be present if value is greater than 0,
MAY be present if 0
X-PROPERTY 0+
ATTACH 0
ATTENDEE 0
CATEGORIES 0
CLASS 0
CONTACT 0
CREATED 0
DESCRIPTION 0
DTEND 0
DTSTART 0
DURATION 0
EXDATE 0
EXRULE 0
GEO 0
LAST-MODIFIED 0
LOCATION 0
PRIORITY 0
RDATE 0
RELATED-TO 0
RESOURCES 0
RRULE 0
STATUS 0
SUMMARY 0
TRANSP 0
URL 0
X-COMPONENT 0+
VTODO 0
VJOURNAL 0
VFREEBUSY 0
VTIMEZONE 0
VALARM 03.3 Methods For VFREEBUSY Components ✨
okay so this section is where we get into the methods for the "VFREEBUSY" calendar component 💖 every method gets its own restriction table, which is basically a checklist of what's in, what's optional, and what's a total no-go 🎀
quick heads up: this document only covers transferring busy time info 🫶 if an app wants free time info, it MUST infer that from the busy time info it already has. no cap, that's the whole deal 🧚
busy time info can be split across more than one "VFREEBUSY" component, which is giving main character organization 🗓️ like grouping by a calendar week, month, or year 🌸 when you do that, each "VFREEBUSY" component MUST include the "ATTENDEE", "DTSTART" and "DTEND" properties, so everyone knows who the busy time came from and what date and time interval it covers ✨
the "FREEBUSY" property value MAY include a list of values, separated by the COMMA character ([US-ASCII] decimal 44). or you can specify multiple busy time periods with multiple instances of the "FREEBUSY" property. both forms MUST be supported by implementations that conform to this document 💅 duplicate busy time periods SHOULD NOT be specified in an iCalendar object 🙈 however, two different busy time periods MAY overlap, and that's totally fine 🦋
"FREEBUSY" properties should be sorted so their values go in ascending order, based on the start time and then the end time, with the earliest periods first 🍓 for example, today's busy time info should show up after yesterday's, and the busy time for this half-hour should come after the busy time for earlier today ⭐
events can span a day boundary, so a free busy time period can span one too 🌙 say individual "A" requests busy time from individuals "B", "C" and "D". individuals "B" and "C" reply to "A" with busy time data 💜 individual "D" doesn't support busy time requests, so it doesn't reply with any data. if the transport binding supports exception messages, then "D" returns an "unsupported capability" message to individual "A4.34.3" 😭
here's the quick summary of the methods defined for the "VFREEBUSY" calendar component 👑
|================|==================================================|
| Method | Description |
|================|==================================================|
| PUBLISH | Publish unsolicited busy time data. |
| REQUEST | Request busy time data. |
| REPLY | Reply to a busy time request. |
|================|==================================================|3.3.1 PUBLISH
the "PUBLISH" method in a "VFREEBUSY" calendar component is how you publish busy time data 📣 it can go from one CU to any other CU 💖 the whole point is sending unsolicited busy time data, which means it is NOT a response to a "REQUEST" method. no invite needed, just vibes ✨
the "ATTENDEE" property must be specified in the busy time information. its value is the CU address of whoever originated the busy time info 🎀
this method type is an iCalendar object that follows these property constraints 🌸
Component/Property Presence
------------------- ----------------------------------------------
METHOD 1 MUST be "PUBLISH"
VFREEBUSY 1+
DTSTAMP 1
DTSTART 1 DateTime values must be in UTC
DTEND 1 DateTime values must be in UTC
FREEBUSY 1+ MUST be BUSYTIME. Multiple instances are
allowed. Multiple instances must be sorted
in ascending order
ORGANIZER 1 MUST contain the address of originator of
busy time data.
COMMENT 0 or 1
CONTACT 0+
X-PROPERTY 0+
URL 0 or 1 Specifies busy time URL
ATTENDEE 0
DURATION 0
REQUEST-STATUS 0
UID 0
X-COMPONENT 0+
VEVENT 0
VTODO 0
VJOURNAL 0
VTIMEZONE 0
VALARM 03.3.2 REQUEST
the "REQUEST" method in a "VFREEBUSY" calendar component is how a "Calendar User" asks for their busy time info 🙋♀️ the request can be for busy time info bounded by a specific date and time interval, which is so specific and so iconic 🔥
this message only lets you request busy time info, nothing else 💅 it's sent from the "Calendar User" asking for the info to one or more intended recipients 🫶
if the originator of the "REQUEST" method isn't authorized to make a busy time request on the recipient's calendar system, then an exception message SHOULD be returned in a "REPLY" method 🙈 but no busy time data needs to come back with it 🌈
this method type is an iCalendar object that follows these property constraints 🍓
Component/Property Presence
------------------- ----------------------------------------------
METHOD 1 MUST be "REQUEST"
VFREEBUSY 1
ATTENDEE 1+ contain the address of the calendar store
DTEND 1 DateTime values must be in UTC
DTSTAMP 1
DTSTART 1 DateTime values must be in UTC
ORGANIZER 1 MUST be the request originator's address
UID 1
COMMENT 0 or 1
CONTACT 0+
X-PROPERTY 0+
FREEBUSY 0
DURATION 0
REQUEST-STATUS 0
URL 0
X-COMPONENT 0+
VALARM 0
VEVENT 0
VTODO 0
VJOURNAL 0
VTIMEZONE 03.3.3 REPLY
the "REPLY" method in a "VFREEBUSY" calendar component is the response to a busy time request 💌 it gets sent by the recipient of the request back to the originator, aka the reply-back moment 🦋
the "REPLY" method may also be used to respond to an unsuccessful "REQUEST" method 🥲 depending on the "REQUEST-STATUS" value, there might be no busy time info sent back at all 💀
this method type is an iCalendar object that follows these property constraints ✨
Component/Property Presence
------------------- ----------------------------------------------
METHOD 1 MUST be "REPLY"
VFREEBUSY 1
ATTENDEE 1 (address of recipient replying)
DTSTAMP 1
DTEND 1 DateTime values must be in UTC
DTSTART 1 DateTime values must be in UTC
FREEBUSY 1+ (values MUST all be of the same data
type. Multiple instances are allowed.
Multiple instances MUST be sorted in
ascending order. Values MAY NOT overlap)
ORGANIZER 1 MUST be the request originator's address
UID 1
COMMENT 0 or 1
CONTACT 0+
REQUEST-STATUS 0+
URL 0 or 1 (specifies busy time URL)
X-PROPERTY 0+
DURATION 0
SEQUENCE 0
X-COMPONENT 0+
VALARM 0
VEVENT 0
VTODO 0
VJOURNAL 0
VTIMEZONE 03.4 Methods For VTODO Components 🧚
this section defines the property set for the methods that work with the "VTODO" calendar component 🌷 each method gets a restriction table that spells out the property constraints for that particular method 💖
here's the quick rundown of the methods defined for the "VTODO" calendar component 👑
+================+==================================================+
| Method | Description |
|================+==================================================|
| PUBLISH | Post notification of a VTODO. Used primarily as |
| | a method of advertising the existence of a VTODO.|
| | |
| REQUEST | Assign a VTODO. This is an explicit assignment to|
| | one or more Calendar Users. The REQUEST method |
| | is also used to update or change an existing |
| | VTODO. Clients that cannot handle REQUEST MAY |
| | degrade the method to treat it as a PUBLISH. |
| | |
| REPLY | Reply to a VTODO request. Attendees MAY set |
| | PARTSTAT to ACCEPTED, DECLINED, TENTATIVE, |
| | DELEGATED, PARTIAL, and COMPLETED. |
| | |
| ADD | Add one or more instances to an existing to-do. |
| | |
| CANCEL | Cancel one or more instances of an existing |
| | to-do. |
| | |
| REFRESH | A request sent to a VTODO Organizer asking for |
| | the latest version of a VTODO. |
| | |
| COUNTER | Counter a REQUEST with an alternative proposal. |
| | |
| DECLINECOUNTER | Decline a counter proposal by an Attendee. |
+================+==================================================+3.4.1 PUBLISH
the "PUBLISH" method in a "VTODO" calendar component has no associated response 🤷♀️ it's basically just posting an iCalendar object that may be added to a calendar 📅 it MUST have an "Organizer" 🫶 and it MUST NOT have "Attendees" 🚫 the expected usage is encapsulating an arbitrary "VTODO" calendar component as an iCalendar object 🎁
the "Organizer" MAY later update a previously published "VTODO" calendar component (with another "PUBLISH" method) 🔄 add instances to it (with an "ADD" method) ➕ or cancel it (with a "CANCEL" method) ❌ iconic organizer behavior 👑
this method type is an iCalendar object that follows these property constraints 🌈
Component/Property Presenceokay bestie, the PUBLISH table is still going 📋
METHOD 1 MUST be "PUBLISH"
VTODO 1+
DTSTAMP 1
DTSTART 1
ORGANIZER 1
PRIORITY 1
SEQUENCE 0 or 1 MUST be present if value is greater than
0, MAY be present if 0
SUMMARY 1 Can be null.
UID 1
ATTACH 0+
CATEGORIES 0 or 1 This property may contain a list of values
CLASS 0 or 1
COMMENT 0 or 1
CONTACT 0+
CREATED 0 or 1
DESCRIPTION 0 or 1 Can be null
DUE 0 or 1 If present DURATION MUST NOT be present
DURATION 0 or 1 If present DUE MUST NOT be present
EXDATE 0+
EXRULE 0+
GEO 0 or 1
LAST-MODIFIED 0 or 1
LOCATION 0 or 1
PERCENT-COMPLETE 0 or 1
RDATE 0+
RECURRENCE-ID 0 or 1 MUST only if referring to an instance of a
recurring calendar component. Otherwise
it MUST NOT be present.
RELATED-TO 0+
RESOURCES 0 or 1 This property may contain a list of values
RRULE 0+
STATUS 0 or 1 MAY be one of COMPLETED/NEEDS ACTION/IN-
PROCESS/CANCELLED
URL 0 or 1
X-PROPERTY 0+
ATTENDEE 0
REQUEST-STATUS 0
VTIMEZONE 0+ MUST be present if any date/time refers to
a timezone
VALARM 0+
X-COMPONENT 0+
VFREEBUSY 0
VEVENT 0
VJOURNAL 03.4.2 REQUEST ✨
okay so, REQUEST in a VTODO is literally the multitasker of the group 💅 It does a bunch of scheduling jobs:
- Assign a to-do to one or more "Calendar Users";
- Reschedule an existing to-do;
- Update the details of an existing to-do, without rescheduling it;
- Update the completion status of "Attendees" of an existing to-do, without rescheduling it;
- Reconfirm an existing to-do, without rescheduling it;
- Delegate/reassign an existing to-do to another "Calendar User".
The assigned "Calendar Users" show up in the "VTODO" calendar component as individual ATTENDEE;ROLE=REQ-PARTICIPANT property value sequences. the main character list 🎀
The originator of a "REQUEST" is the "Organizer" of the to-do. The recipient is the "Calendar User" who got assigned the to-do 🫶 The "Attendee" uses the "REPLY" method to share their acceptance and completion status with the "Organizer" of the "REQUEST".
The "UID", "SEQUENCE", and "DTSTAMP" properties are how everyone tells the different "REQUEST" vibes apart 🔍 If the "UID" property value in the "REQUEST" isn't on the recipient's calendar, then it's a brand new to-do ✨ If the "UID" property value is on the recipient's calendar, then the "REQUEST" is a rescheduling, an update, or a reconfirm of the "VTODO" calendar object. so iconic 🦋
If the "Organizer" of the "REQUEST" method isn't authorized to make a to-do request on the "Attendee's" calendar system, then an exception comes back in the "REQUEST-STATUS" property of a later "REPLY" method, but no scheduling action happens 🙈 not allowed, sorry bestie 💀
For the "REQUEST" method, multiple "VTODO" components in a single iCalendar object are only permitted when they share the same "UID" property. So a series of recurring events can carry instance-specific info, and in that case, you need multiple "VTODO" components to express the entire series 🌈
This method type is an iCalendar object that follows these property constraints:
Component/Property Presence
------------------- ----------------------------------------------
METHOD 1 MUST be "REQUEST"
VTODO 1+ All components must have the same UID
ATTENDEE 1+
DTSTAMP 1
DTSTART 1
ORGANIZER 1
PRIORITY 1
SEQUENCE 0 or 1 MUST be present if value is greater than
0, MAY be present if 0
SUMMARY 1 Can be null.
UID 1
ATTACH 0+
CATEGORIES 0 or 1 This property may contain a list of
values
CLASS 0 or 1
COMMENT 0 or 1
CONTACT 0+
CREATED 0 or 1
DESCRIPTION 0 or 1 Can be null
DUE 0 or 1 If present DURATION MUST NOT be present
DURATION 0 or 1 If present DUE MUST NOT be present
EXDATE 0+
EXRULE 0+
GEO 0 or 1
LAST-MODIFIED 0 or 1
LOCATION 0 or 1
PERCENT-COMPLETE 0 or 1
RDATE 0+
RECURRENCE-ID 0 or 1 present if referring to an instance of a
recurring calendar component. Otherwise
it MUST NOT be present.
RELATED-TO 0+
RESOURCES 0 or 1 This property may contain a list of
values
RRULE 0+
STATUS 0 or 1 MAY be one of COMPLETED/NEEDS ACTION/IN-
PROCESS
URL 0 or 1
X-PROPERTY 0+
REQUEST-STATUS 0
VALARM 0+
VTIMEZONE 0+ MUST be present if any date/time refers
to a timezone
X-COMPONENT 0+
VEVENT 0
VFREEBUSY 0
VJOURNAL 03.4.2.1 REQUEST for Rescheduling a VTODO
rescheduling era 🗓️ The "REQUEST" method can be used to reschedule a "VTODO" calendar component.
Rescheduling a "VTODO" calendar component means changing the existing one's start or due time, its recurrence intervals, and possibly the description ✨ If the recipient CUA of a "REQUEST" method sees that the "UID" property value already exists on the calendar, but the "SEQUENCE" property value in the "REQUEST" is greater than the value for the existing VTODO, then the "REQUEST" method describes a rescheduling of the "VTODO" calendar component. the SEQUENCE number is doing the heavy lifting here 🔥
3.4.2.2 REQUEST for Update or Reconfirmation of a VTODO
the quiet glow-up era 🌸 The "REQUEST" method can be used to update or reconfirm a "VTODO" calendar component. Reconfirmation is basically just an update to the "Attendee" completion status or the overall "VTODO" calendar component status.
An update to an existing "VTODO" calendar component doesn't touch the start or due time or recurrence intervals, and usually doesn't touch the description either 🙅♀️ If the recipient CUA of a "REQUEST" method sees that the "UID" property value already exists on the calendar, and the "SEQUENCE" property value in the "REQUEST" matches the value for the existing event, then the "REQUEST" method describes an update of the "VTODO" calendar component details, but not a rescheduling.
The update "REQUEST" is the right reply to a "REFRESH" method that an "Attendee" sends to the "Organizer" of a "VTODO" calendar component 💖
Unsolicited "REQUEST" methods MAY be sent by the "Organizer" of a "VTODO" calendar component 🧚 These unsolicited ones are used to update the details of the "VTODO" (without rescheduling it or changing the completion status of "Attendees"), or to update the "VTODO" calendar component itself (i.e., reconfirm the "VTODO").
3.4.2.3 REQUEST for Delegating a VTODO
passing the baton era 🏃♀️💨 The "REQUEST" method is also used to delegate or reassign ownership of a "VTODO" calendar component to another "Calendar User". For example, it can be used to hand off an "Attendee's" role (i.e. "chair", or "participant") for a "VTODO" calendar component. The "REQUEST" method gets sent by one of the "Attendees" of an existing "VTODO" calendar component to some other individual. An "Attendee" of a "VTODO" calendar component MUST NOT delegate to the "Organizer" of the event. nope nope, not the boss 🙅♀️
For this section, the "Attendee" doing the delegating is called the "Delegator". The "Attendee" getting the delegation request is called the "Delegate" 🫶
The "Delegator" of a "VTODO" calendar component MUST forward the existing "REQUEST" method for that "VTODO" calendar component to the "Delegate". The "VTODO" calendar component description MUST include the "Delegator's" up-to-date "VTODO" calendar component definition. The "REQUEST" method MUST also include an "ATTENDEE" property with the calendar address of the "Delegate". The "Delegator" MUST also send a "REPLY" method back to the "Organizer", with the "Delegator's" "Attendee" property "partstat" parameter value set to "DELEGATED". On top of that, the "delegated-to" parameter MUST be included with the calendar address of the "Delegate". A response to the delegation "REQUEST" goes from the "Delegate" to the "Organizer" and, optionally, to the "Delegator". The "REPLY" method from the "Delegate" SHOULD include the "ATTENDEE" property with their calendar address and the "delegated-from" parameter with the value of the "Delegator's" calendar address. so many parameters, I'm obsessed 🤓✨
The delegation "REQUEST" method MUST assign a value for the "RSVP" property parameter on the "Delegator's" "Attendee" property, matching the "Delegate's" "ATTENDEE" property. For example, if the "Delegator's" "ATTENDEE" property specifies "RSVP=TRUE", then the "Delegate's" "ATTENDEE" property MUST specify "RSVP=TRUE". 🦋
3.4.2.4 REQUEST Forwarded To An Uninvited Calendar User
the plus-one who wasn't invited 👀 An "Attendee" assigned a "VTODO" calendar component may send the "VTODO" calendar component to another new CU, one that wasn't previously associated with the "VTODO" calendar component. The current "Attendee" does this by forwarding the original "REQUEST" method to the new CU. The new CU can send a "REPLY" to the "Organizer" of the "VTODO" calendar component, and that reply contains an "ATTENDEE" property for the new CU.
The "Organizer" has the final say on whether the new CU becomes part of the to-do, and they don't owe the uninvited CU anything with a "REPLY" from them 💅 If the "Organizer" doesn't want the new CU in the to-do, the new "ATTENDEE" property doesn't get added to the "VTODO" calendar component. The "Organizer" MAY send the CU a "CANCEL" message to say they won't be added to the to-do. If the "Organizer" does decide to add the new CU, then the new "ATTENDEE" property gets added to the "VTODO" calendar component. Plus, the "Organizer" is free to change any "ATTENDEE" property parameter from what the new CU supplied to whatever the "Organizer" thinks is appropriate ✨ the organizer really holds the mic here 🎤
3.4.2.5 REQUEST Updated Attendee Status
the little check-in 💬 An "Organizer" of a "VTODO" may ask for an updated status from one or more "Attendees" 🥹 The "Organizer" sends a "REQUEST" method to the "Attendee" with the ATTENDEE;RSVP=TRUE property sequence. The "SEQUENCE" property for the "VTODO" is left at its previous value. A recipient figures out that the only change in the "REQUEST" is their "RSVP" property parameter asking for an updated status. The recipient SHOULD respond with a "REPLY" method showing their current status with respect to the "REQUEST" 🌈 bestie, reply back, no ghosting 💜
3.4.3 REPLY ✨
okay so REPLY in a VTODO is how an attendee talks back, like accepting or declining a request, answering a delegation, or updating how done their to-do is 💅 when it's a delegation response, the Delegator MUST include the Delegate's calendar address in the delegated-to parameter of the Delegator's ATTENDEE property. the Delegate MUST include the Delegator's calendar address in the delegated-from parameter of the Delegate's ATTENDEE property. the whole handshake is giving paper trail 🧚
REPLY MAY also be used to respond to a REQUEST for a VTODO that didn't go through. depending on the REQUEST-STATUS value, it's possible nothing got scheduled at all 🙈
the Organizer of a VTODO MAY get a REPLY from someone who wasn't in the original REQUEST. like, a REPLY MAY come from a Delegate of the VTODO. and the REPLY MAY also come from an unknown Calendar User who got the REQUEST forwarded to them by an original Attendee 👀 that uninvited attendee MAY be accepted, or the Organizer MAY cancel the VTODO for them by sending a CANCEL method. main character energy from the organizer, honestly 👑
this method type is an iCalendar object that follows these property rules:
Component/Property Presence
------------------- ---------------------------------------------
METHOD 1 MUST be "REPLY"
VTODO 1+ All component MUST have the same UID
ATTENDEE 1+
DTSTAMP 1
ORGANIZER 1
REQUEST-STATUS 1+
UID 1 MUST must be the address of the replying
attendee
ATTACH 0+
CATEGORIES 0 or 1 This property may contain a list of values
CLASS 0 or 1
COMMENT 0 or 1
CONTACT 0+
CREATED 0 or 1
DESCRIPTION 0 or 1
DTSTART 0 or 1
DUE 0 or 1 If present DURATION MUST NOT be present
DURATION 0 or 1 If present DUE MUST NOT be present
EXDATE 0+
EXRULE 0+
GEO 0 or 1
LAST-MODIFIED 0 or 1
LOCATION 0 or 1
PERCENT-COMPLETE 0 or 1
PRIORITY 0 or 1
RDATE 0+
RELATED-TO 0+
RESOURCES 0 or 1 This property may contain a list of values
RRULE 0+
RECURRENCE-ID 0 or 1 MUST only if referring to an instance of a
Recurring calendar component. Otherwise it
MUST NOT be present
SEQUENCE 0 or 1 MUST be the sequence number of
the original REQUEST if greater than 0.
MAY be present if 0.
STATUS 0 or 1
SUMMARY 0 or 1 Can be null
URL 0 or 1
X-PROPERTY 0+
VTIMEZONE 0 or 1 MUST be present if any date/time refers to
a timezone
X-COMPONENT 0+
VALARM 0
VEVENT 0
VFREEBUSY 03.4.4 ADD 🎀
the ADD method in a VTODO is for adding one or more instances to an existing to-do, so it's basically the "oh wait, one more thing" text 💌
if the UID value in the ADD isn't on the recipient's calendar, the recipient SHOULD send a REFRESH to the Organizer so they can get the newest version of the VTODO 🔄 and if an Attendee implementation doesn't support the ADD method, it should respond with a REQUEST-STATUS value of 5.3 and ask for a REFRESH 🙏
the SEQUENCE value gets incremented, since the to-dos have changed 🔢
this method type is an iCalendar object that follows these property rules:
Component/Property Presence
------------------- ----------------------------------------------
METHOD 1 MUST be "ADD"
VTODO 1
DTSTAMP 1
ORGANIZER 1
PRIORITY 1
SEQUENCE 1 MUST be greater than 0
SUMMARY 1 Can be null.
UID 1 MUST match that of the original to-do
ATTACH 0+
ATTENDEE 0+
CATEGORIES 0 or 1 This property may contain a list of
values
CLASS 0 or 1
COMMENT 0 or 1
CONTACT 0+
CREATED 0 or 1
DESCRIPTION 0 or 1 Can be null
DTSTART 0 or 1
DUE 0 or 1 If present DURATION MUST NOT be present
DURATION 0 or 1 If present DUE MUST NOT be present
EXDATE 0+
EXRULE 0+
GEO 0 or 1
LAST-MODIFIED 0 or 1
LOCATION 0 or 1
PERCENT-COMPLETE 0 or 1
RDATE 0+
RELATED-TO 0+
RESOURCES 0 or 1 This property may contain a list of
values
RRULE 0+
STATUS 0 or 1 MAY be one of COMPLETED/NEEDS ACTION/IN-
PROCESS
URL 0 or 1
X-PROPERTY 0+
RECURRENCE-ID 0
REQUEST-STATUS 0
VALARM 0+
VTIMEZONE 0+ MUST be present if any date/time refers
to a timezone
X-COMPONENT 0+
VEVENT 0
VJOURNAL 0
VFREEBUSY 03.4.5 CANCEL 🚫
the CANCEL method in a VTODO sends a cancellation notice for an existing VTODO request to the Attendees 💔 only the Organizer sends it, and it goes out to the Attendees of that VTODO. for a recurring VTODO, you can cancel the whole thing or just some instances. to cancel the full range of a recurring VTODO, the UID value for the VTODO MUST be specified, and a RECURRENCE-ID MUST NOT be specified in the CANCEL method. to cancel one individual instance of a recurring VTODO, the RECURRENCE-ID value for the VTODO MUST be specified in the CANCEL method 🥺
there are two ways to cancel a sequence of instances of a recurring VTODO:
(a) the RECURRENCE-ID property for an instance in the sequence MUST be specified with the RANGE property parameter value of THISANDPRIOR (or THISANDFUTURE) to indicate cancellation of the specified VTODO and all instances before (or after); or
(b) individual recurrence instances may be cancelled by specifying multiple RECURRENCE-ID properties corresponding to the instances to be cancelled.
when a VTODO gets cancelled, the SEQUENCE value MUST be incremented 🔢
this method type is an iCalendar object that follows these property rules:
Component/Property Presence
------------------- ---------------------------------------------
METHOD 1 MUST be "CANCEL"
VTODO 1
ATTENDEE 0+ include all "Attendees" being removed from
the todo. MUST include all "Attendees" if
the entire todo is cancelled.
UID 1 MUST echo original UID
DTSTAMP 1
ORGANIZER 1
SEQUENCE 1
ATTACH 0+
CATEGORIES 0 or 1 This property MAY contain a list of values
CLASS 0 or 1
COMMENT 0 or 1
CONTACT 0+
CREATED 0 or 1
DESCRIPTION 0 or 1
DTSTART 0 or 1
DUE 0 or 1 If present DURATION MUST NOT be present
DURATION 0 or 1 If present DUE MUST NOT be present
EXDATE 0+
EXRULE 0+
GEO 0 or 1
LAST-MODIFIED 0 or 1
LOCATION 0 or 1
PERCENT-COMPLETE 0 or 1
RDATE 0+
RECURRENCE-ID 0 or 1 MUST only if referring to one or more
instances of a recurring calendar
component. Otherwise it MUST NOT be
present.
RELATED-TO 0+
RESOURCES 0 or 1 This property MAY contain a list of values
RRULE 0+
PRIORITY 0 or 1
STATUS 0 or 1 If present it MUST be set to "CANCELLED".
MUST NOT be used if purpose is to remove
"ATTENDEES" rather than cancel the entire
VTODO.
URL 0 or 1
X-PROPERTY 0+
REQUEST-STATUS 0
VTIMEZONE 0 or 1 MUST be present if any date/time refers to
a timezone
X-COMPONENT 0+
VALARM 0
VEVENT 0
VFREEBUSY 03.4.6 REFRESH 🔄
the REFRESH method in a VTODO is how Attendees ask the Organizer for an updated description of an existing VTODO 🫶 the Organizer MAY also use it to ask the Attendees for an updated status. the REFRESH method MUST specify the UID property for the VTODO that needs updating ✨
you can request a refresh of one recurrence instance by specifying the RECURRENCE-ID property for the matching VTODO. the Organizer responds with the latest description and rendition of the VTODO. usually that comes back as a REQUEST, unless the VTODO got cancelled, in which case the ORGANIZER MUST send a CANCEL 💀 this method is meant to make it easy for machines to ask for updates to a VTODO 🤖
this method type is an iCalendar object that follows these property rules:
Component/Property Presence
------------------- ---------------------------------------------
METHOD 1 MUST be "REFRESH"
VTODO 1
ATTENDEE 1
DTSTAMP 1
UID 1 MUST echo original UID
RECURRENCE-ID 0 or 1 MUST only if referring to an instance of a
Recurring calendar component. Otherwise it
MUST NOT be present
X-PROPERTY 0+
ATTACH 0
CATEGORIES 0
CLASS 0
COMMENT 0
CONTACT 0
CREATED 0
DESCRIPTION 0
DTSTART 0
DUE 0
DURATION 0
EXDATE 0
EXRULE 0
GEO 0
LAST-MODIFIED 0
LOCATION 0
ORGANIZER 0
PERCENT-COMPLETE 0
PRIORITY 0
RDATE 0
RELATED-TO 0
REQUEST-STATUS 0
RESOURCES 0
RRULE 0
SEQUENCE 0
STATUS 0
URL 0
X-COMPONENT 0+
VALARM 0
VEVENT 0
VFREEBUSY 0
VTIMEZONE 03.4.7 COUNTER 💌
okay bestie, so the COUNTER method in a VTODO calendar component is how an Attendee of an existing VTODO slides into the Organizer's DMs with a counter proposal. it gets sent to the Organizer of that VTODO, obviously 💅
the counter proposal is an iCalendar object made of a VTODO that fully describes the alternate VTODO. like, the complete description, not just vibes ✨
the Organizer can say no by sending the Attendee a DECLINECOUNTER method. or they can say yes by sending ALL the Attendees a REQUEST method that reschedules the VTODO. if they go with the yes route, the Organizer SHOULD reset the individual RSVP parameter values to TRUE on each ATTENDEE property, so everyone is forced to respond 🫶
this method type is an iCalendar object that conforms to the following property constraints:
Component/Property Presence
------------------- ----------------------------------------------
METHOD 1 MUST be "COUNTER"
VTODO 1
ATTENDEE 1+
DTSTAMP 1
ORGANIZER 1
PRIORITY 1
SUMMARY 1 Can be null
UID 1
ATTACH 0+
CATEGORIES 0 or 1 This property MAY contain a list of values
CLASS 0 or 1
COMMENT 0 or 1
CONTACT 0+
CREATED 0 or 1
DESCRIPTION 0 or 1 Can be null
DTSTART 0 or 1
DUE 0 or 1 If present DURATION MUST NOT be present
DURATION 0 or 1 If present DUE MUST NOT be present
EXDATE 0+
EXRULE 0+
GEO 0 or 1
LAST-MODIFIED 0 or 1
LOCATION 0 or 1
PERCENT-COMPLETE 0 or 1
RDATE 0+
RECURRENCE-ID 0 or 1 MUST only 3.5if referring to an instance of a
recurring calendar component. Otherwise it
MUST NOT be present.
RELATED-TO 0+
REQUEST-STATUS 0+
RESOURCES 0 or 1 This property MAY contain a list of values
RRULE 0 or 1
SEQUENCE 0 or 1 MUST echo the original SEQUENCE number.
MUST be present if non-zero. MAY be present
if zero.
STATUS 0 or 1 MAY be one of COMPLETED/NEEDS ACTION/IN-
PROCESS/CANCELLED
URL 0 or 1
X-PROPERTY 0+
VALARM 0+
VTIMEZONE 0 or 1 MUST be present if any date/time refers to
a timezone
X-COMPONENT 0+
VEVENT 0
VFREEBUSY 03.4.8 DECLINECOUNTER 🙅
the DECLINECOUNTER method in a VTODO calendar component is used by an Organizer of a VTODO calendar component to reject a counter proposal offered by one of the Attendees. the Organizer sends the message to the Attendee that sent the COUNTER method to the Organizer. so it's a polite "nah, not this one" 🥺
this method type is an iCalendar object that conforms to the following property constraints:
Component/Property Presence
------------------- ---------------------------------------------
METHOD 1 MUST be "DECLINECOUNTER"
VTODO 1
ATTENDEE 1+ MUST for all attendees
DTSTAMP 1
ORGANIZER 1
SEQUENCE 1 MUST echo the original SEQUENCE number
UID 1 MUST echo original UID
ATTACH 0+
CATEGORIES 0 or 1 This property may contain a list of values
CLASS 0 or 1
COMMENT 0 or 1
CONTACT 0+
CREATED 0 or 1
DESCRIPTION 0 or 1
DTSTART 0 or 1
DUE 0 or 1 If present DURATION MUST NOT be present
DURATION 0 or 1 If present DUE MUST NOT be present
EXDATE 0+
EXRULE 0+
GEO 0 or 1
LAST-MODIFIED 0 or 1
LOCATION 0 or 1
PERCENT-COMPLETE 0 or 1
PRIORITY 0 or 1
RDATE 0+
RECURRENCE-ID 0 or 1 MUST only if referring to an instance of a
recurring calendar component. Otherwise
it MUST NOT be present.
RELATED-TO 0+
REQUEST-STATUS 0+
RESOURCES 0 or 1 This property MAY contain a list of values
RRULE 0+
STATUS 0 or 1 MAY be one of COMPLETED/NEEDS ACTION/IN-
PROCESS
URL 0 or 1
X-PROPERTY 0+
VTIMEZONE 0+ MUST be present if any date/time refers to
a timezone
X-COMPONENT 0+
VALARM 0
VEVENT 0
VFREEBUSY 03.5 Methods For VJOURNAL Components 📓
this section is all about the property sets for the methods that work with the VJOURNAL calendar component. it's giving journal era 🦋
here's the quick lineup of the methods defined for VJOURNAL:
+================+==================================================+
| Method | Description |
|================+==================================================|
| PUBLISH | Post a journal entry. Used primarily as a method |
| | of advertising the existence of a journal entry. |
| | |
| ADD | Add one or more instances to an existing journal |
| | entry. |
| | |
| CANCEL | Cancel one or more instances of an existing |
| | journal entry. |
+================+==================================================+3.5.1 PUBLISH 📣
the PUBLISH method in a VJOURNAL calendar component has no associated response. it's basically a post that just gets dropped onto a calendar, no replies needed 🌸 it MUST have an Organizer, and it MUST NOT have Attendees. the main use is wrapping up an arbitrary journal entry as an iCalendar object. the Organizer MAY later update it (with another PUBLISH method) or cancel it (with a CANCEL method) if the journal entry was already published 💜
this method type is an iCalendar object that conforms to the following property constraints:
Component/Property Presence
------------------- ----------------------------------------------
METHOD 1 MUST be "PUBLISH"
VJOURNAL 1+
DESCRIPTION 1 Can be null.
DTSTAMP 1
DTSTART 1
ORGANIZER 1
UID 1
ATTACH 0+
CATEGORIES 0 or 1 This property MAY contain a list of values
CLASS 0 or 1
COMMENT 0 or 1
CONTACT 0+
CREATED 0 or 1
EXDATE 0+
EXRULE 0+
LAST-MODIFIED 0 or 1
RDATE 0+
RECURRENCE-ID 0 or 1 MUST only if referring to an instance of a
recurring calendar component. Otherwise
it MUST NOT be present.
RELATED-TO 0+
RRULE 0+
SEQUENCE 0 or 1 MUST echo the original SEQUENCE number.
MUST be present if non-zero. MAY be
present if zero.
STATUS 0 or 1 MAY be one of DRAFT/FINAL/CANCELLED
SUMMARY 0 or 1 Can be null
URL 0 or 1
X-PROPERTY 0+
ATTENDEE 0
VALARM 0+
VTIMEZONE 0+ MUST be present if any date/time refers to
a timezone
X-COMPONENT 0+
VEVENT 0
VFREEBUSY 0
VTODO 03.5.2 ADD ➕
the ADD method in a VJOURNAL calendar component is used to add one or more instances to an existing VJOURNAL entry. there's no response going back to the Organizer 🙌
if the UID property value in the ADD isn't found on the recipient's calendar, then the recipient MAY treat the ADD as a PUBLISH. a little glow-up backup plan ✨
this method type is an iCalendar object that conforms to the following property constraints:
Component/Property Presence
------------------- ----------------------------------------------
METHOD 1 MUST be "ADD"
VJOURNAL 1
DESCRIPTION 1 Can be null.
DTSTAMP 1
DTSTART 1
ORGANIZER 1
SEQUENCE 1 MUST be greater than 0
UID 1 MUST match that of the original journal
ATTACH 0+
CATEGORIES 0 or 1 This property MAY contain a list of values
CLASS 0 or 1
COMMENT 0 or 1
CONTACT 0+
CREATED 0 or 1
EXDATE 0+
EXRULE 0+
LAST-MODIFIED 0 or 1
RDATE 0+
RELATED-TO 0+
RRULE 0+
STATUS 0 or 1 MAY be one of DRAFT/FINAL/CANCELLED
SUMMARY 0 or 1 Can be null
URL 0 or 1
X-PROPERTY 0+
ATTENDEE 0
RECURRENCE-ID 0
VALARM 0+
VTIMEZONE 0 or 1 MUST be present if any date/time refers to
a timezone
X-COMPONENT 0+
VEVENT 0
VFREEBUSY 0
VTODO 03.5.3 CANCEL 🚫
the CANCEL method in a VJOURNAL calendar component is used to send a cancellation notice for an existing journal entry. the Organizer of the journal entry is the one who sends it. for a recurring journal entry, you can cancel either the whole thing or just some instances of it 🍓 to cancel the complete range of a recurring journal entry, the UID property value for the journal entry MUST be specified, and a RECURRENCE-ID property MUST NOT be specified in the CANCEL method. to cancel one individual instance instead, the RECURRENCE-ID property value for the journal entry MUST be specified in the CANCEL method.
there are two options for canceling a sequence of instances of a recurring VJOURNAL calendar component:
(a) the RECURRENCE-ID property for an instance in the sequence MUST be specified with the RANGE property parameter value of THISANDPRIOR (or THISANDFUTURE) to indicate cancellation of the specified "VTODO" calendar component and all instances before (or after); or
(b) individual recurrence instances may be cancelled by specifying multiple RECURRENCE-ID properties corresponding to the instances to be cancelled.
when a VJOURNAL is cancelled, the SEQUENCE property value MUST be incremented 📈
this method type is an iCalendar object that conforms to the following property constraints:
Component/Property Presence
METHOD 1 MUST be "CANCEL" VJOURNAL 1+ All MUST have the same UID DTSTAMP 1 ORGANIZER 1 SEQUENCE 1 UID 1 MUST be the UID of the original REQUEST
ATTACH 0+ ATTENDEE 0+ CATEGORIES 0 or 1 This property MAY contain a list of values CLASS 0 or 1 COMMENT 0 or 1 CONTACT 0+ CREATED 0 or 1 DESCRIPTION 0 or 1 DTSTART 0 or 1 EXDATE 0+ EXRULE 0+ LAST-MODIFIED 0 or 1 RDATE 0+ RECURRENCE-ID 0 or 1 only if referring to an instance of a recurring calendar component. Otherwise it MUST NOT be present. RELATED-TO 0+ RRULE 0+ STATUS 0 or 1 MAY be present, must be "CANCELLED" if present SUMMARY 0 or 1 URL 0 or 1 X-PROPERTY 0+ REQUEST-STATUS 0
VTIMEZONE 0+ MUST be present if any date/time refers to a timezone X-COMPONENT 0+ VALARM 0 VEVENT 0 VFREEBUSY 0 VTODO 0
## 3.6 Status Replies ✨
Okay so here's where the `REQUEST-STATUS` property gets to show off 💅 It can come back carrying one of the codes in the table below, and each code has its own little story to tell 🎀
| ==============+============================+========================= | ||
|---|---|---|
| Short Return | Longer Return Status | Offending Data |
| Status Code | Description | |
| ==============+============================+========================= | ||
| 2.0 | Success. | None. |
| ==============+============================+========================= | ||
| 2.1 | Success but fallback taken | Property name and value |
| on one or more property | MAY be specified. | |
| values. | ||
| ==============+============================+========================= | ||
| 2.2 | Success, invalid property | Property name MAY be |
| ignored. | specified. | |
| ==============+============================+========================= | ||
| 2.3 | Success, invalid property | Property parameter name |
| parameter ignored. | and value MAY be | |
| specified. | ||
| ==============+============================+========================= | ||
| 2.4 | Success, unknown non- | Non-standard property |
| standard property ignored. | name MAY be specified. | |
| ==============+============================+========================= | ||
| 2.5 | Success, unknown non | Property and non- |
| standard property value | standard value MAY be | |
| ignored. | specified. | |
| ==============+============================+========================= | ||
| 2.6 | Success, invalid calendar | Calendar component |
| component ignored. | sentinel (e.g., BEGIN: | |
| ALARM) MAY be | ||
| specified. | ||
| ==============+============================+========================= | ||
| 2.7 | Success, request forwarded | Original and forwarded |
| to Calendar User. | caluser addresses MAY | |
| be specified. | ||
| ==============+============================+========================= | ||
| 2.8 | Success, repeating event | RRULE or RDATE property |
| ignored. Scheduled as a | name and value MAY be | |
| single component. | specified. | |
| ==============+============================+========================= | ||
| 2.9 | Success, truncated end date | DTEND property value |
| time to date boundary. | MAY be specified. | |
| ==============+============================+========================= | ||
| 2.10 | Success, repeating VTODO | RRULE or RDATE property |
| ignored. Scheduled as a | name and value MAY be | |
| single VTODO. | specified. | |
| ==============+============================+========================= | ||
| 2.11 | Success, unbounded RRULE | RRULE property name and |
| clipped at some finite | value MAY be specified. | |
| number of instances | Number of instances MAY | |
| also be specified. | ||
| ==============+============================+========================= | ||
| 3.0 | Invalid property name. | Property name MAY be |
| specified. | ||
| ==============+============================+========================= | ||
| 3.1 | Invalid property value. | Property name and value |
| MAY be specified. | ||
| ==============+============================+========================= | ||
| 3.2 | Invalid property parameter. | Property parameter name |
| and value MAY be | ||
| specified. | ||
| ==============+============================+========================= | ||
| 3.3 | Invalid property parameter | Property parameter name |
| value. | and value MAY be | |
| specified. | ||
| ==============+============================+========================= | ||
| 3.4 | Invalid calendar component | Calendar component |
| sequence. | sentinel MAY be | |
| specified (e.g., BEGIN: | ||
| VTIMEZONE). | ||
| ==============+============================+========================= | ||
| 3.5 | Invalid date or time. | Date/time value(s) MAY |
| be specified. | ||
| ==============+============================+========================= | ||
| 3.6 | Invalid rule. | Rule value MAY be |
| specified. | ||
| ==============+============================+========================= | ||
| 3.7 | Invalid Calendar User. | Attendee property value |
| MAY be specified. | ||
| ==============+============================+========================= | ||
| 3.8 | No authority. | METHOD and Attendee |
| property values MAY be | ||
| specified. | ||
| ==============+============================+========================= | ||
| 3.9 | Unsupported version. | VERSION property name |
| and value MAY be | ||
| specified. | ||
| ==============+============================+========================= | ||
| 3.10 | Request entity too large. | None. |
| ==============+============================+========================= | ||
| 3.11 | Required component or | Component or property |
| property missing. | name MAY be specified. | |
| ==============+============================+========================= | ||
| 3.12 | Unknown component or | Component or property |
| property found | name MAY be specified | |
| ==============+============================+========================= | ||
| 3.13 | Unsupported component or | Component or property |
| property found | name MAY be specified | |
| ==============+============================+========================= | ||
| 3.14 | Unsupported capability | Method or action MAY |
| be specified | ||
| ==============+============================+========================= | ||
| 4.0 | Event conflict. Date/time | DTSTART and DTEND |
| is busy. | property name and values | |
| MAY be specified. | ||
| ==============+============================+========================= | ||
| 5.0 | Request MAY supported. | Method property value |
| MAY be specified. | ||
| ==============+============================+========================= | ||
| 5.1 | Service unavailable. | ATTENDEE property value |
| MAY be specified. | ||
| ==============+============================+========================= | ||
| 5.2 | Invalid calendar service. | ATTENDEE property value |
| MAY be specified. | ||
| ==============+============================+========================= | ||
| 5.3 | No scheduling support for | ATTENDEE property value |
| user. | MAY be specified. | |
| ==============+============================+========================= |
## 3.7 Implementation Considerations ✨
### 3.7.1 Working With Recurrence Instances 🔁
okay so iCalendar has a recurrence grammar 🙌 and it's honestly iconic, because you can represent a whole bunch of events in a **single object** ✨. BUT ngl, meeting instances still need to be referenced 🙈. Like, an "Attendee" might decline the third instance of a recurring Friday event 💀, or the "Organizer" might change the time or location for just ONE instance of the recurring event 📍.
Since implementations can choose to store recurring events as either a single event object or a collection of discreet, related event objects, the protocol is designed so that each recurring instance can be both referenced and versioned 💅. So implementations that want to maintain per-instance properties (like the "partstat" parameter on the "ATTENDEE" property) may do so 🦋. However, the protocol does not require per-instance recognition unless the instance itself has to be renegotiated 🫶.
Here are the scenarios for recurrence instance referencing. To keep things simple, a change to an event refers to a "trigger property" 🔥. That's a property with a substantive effect on the meeting itself, like start time, location, due date (for "VTODO" calendar component components), and possibly description.
"Organizer" initiated actions:
- "Organizer" deletes or changes a single instance of a recurring event
- "Organizer" makes changes that affect all future instances
- "Organizer" makes changes that affect all previous instances
- "Organizer" deletes or modifies a previously changed instance
"Attendee" initiated actions:
- "Attendee" changes status for a particular recurrence instance
- "Attendee" sends Event-Counter for a particular recurrence instance
An instance of a recurring event gets a unique identification, the "RECURRENCE-ID" property, when that instance is renegotiated ✨. Negotiation may be necessary when a substantive change to the event or to-do has be made (such as changing the start time, end time, due date or location). The "Organizer" can identify a specific recurrence instance using the "RECURRENCE-ID" property, and its value is equal to the date/time of the instance. If the "Organizer" wants to change the "DTSTART", the original "DTSTART" value is used for the "RECURRENCE-ID" property, and the new "DTSTART" and "DTEND" values reflect the change. Note that after the change has occurred, the "RECURRENCE-ID" has changed to the new "DTSTART" value 👑.
### 3.7.2 Attendee Property Considerations 🎀
The "ORGANIZER" property is required on published events, to-dos, and journal entries, and there are two reasons for that 💜. First, only the "Organizer" is allowed to update and redistribute an event or to-do component. It follows that the "ORGANIZER" property MUST be present in the event, to-do, or journal entry component so that the CUA has a basis for authorizing an update. Second, it is prudent to provide a point of contact for anyone who receives a published component in case of problems 🫶.
There are valid [RFC-822] addresses that represent groups. Sending email to one of these addresses results in mail being sent to multiple recipients 📬. Such an address may be used as the value of an "ATTENDEE" property. Thus, it is possible that the recipient of a "REQUEST" does not appear explicitly in the list 🙃.
It is recommended that the general approach to finding a "Calendar User" in an attendee list be as follows:
1. Search for the "Calendar User" in the attendee list where "TYPE=INDIVIDUAL"
2. Failing (1), look for attendees where "TYPE=GROUP" or 'TYPE=UNKNOWN'. The CUA then determines if the "Calendar User" is a member of one of these groups. If so, the "REPLY" method sent to the "Organizer" MUST contain a new "ATTENDEE" property in which:
- the "type" property parameter is set to INDIVIDUAL
- the "member" property parameter is set to the name of the group
3. Failing (2), the CUA MAY ignore or accept the request as the "Calendar User" wishes 🤷♀️
### 3.7.3 X-Tokens 🧚
To make iCalendar objects extensible, new property types MAY be inserted into components 🌈. These properties are called X-Tokens, because they are prefixed with "X-" ✨. A client is not required to make sense of X-Tokens. Clients are not required to save X-Tokens or use them in replies, so no stress 🌸.
---
# 4 Examples 🎬
## 4.1 Published Event Examples 📣
In the calendaring and scheduling context, publication refers to the one way transfer of event information 💌. Consumers of published events simply incorporate the event into a calendar, and no reply is expected. Individual "A" publishes an event, and Individual "B" reads the event and incorporates it into their calendar. Events are published in several ways, including embedding the event as an object in a web page, e-mailing the event to a distribution list, and posting the event to a newsgroup 🦋.
The table below illustrates the sequence of events between the publisher and the consumers of a published event 📊.
+-------------------------------------------------------------------+
| Action | "Organizer" |
+---------------------------------+---------------------------------+
| Publish an event | "A" sends or posts a PUBLISH |
|---|---|
| message |
+---------------------------------+---------------------------------+
| "B" reads a published event |
+---------------------------------+---------------------------------+
| Publish an updated event | "A" sends or posts a PUBLISH |
|---|---|
| message |
+---------------------------------+---------------------------------+
| "B" reads the updated event |
+---------------------------------+---------------------------------+
| Cancel a published event | "A" sends or posts a CANCEL |
|---|---|
| message |
+---------------------------------+---------------------------------+
| "B" reads the canceled event | |
|---|---|
| publication |
+---------------------------------+---------------------------------+
### 4.1.1 A Minimal Published Event 🌟
The iCalendar object below describes a single event that begins on July 1, 1997 at 20:00 UTC. This is the minimum set of properties for a "PUBLISH" for a "VEVENT" calendar component 🎀.
BEGIN:VCALENDAR METHOD:PUBLISH PRODID:-//ACME/DesktopCalendar//EN VERSION:2.0 BEGIN:VEVENT ORGANIZER:mailto:a@example.com DTSTART:19970701T200000Z DTSTAMP:19970611T190000Z SUMMARY:ST. PAUL SAINTS -VS- DULUTH-SUPERIOR DUKES UID:0981234-1234234-23@example.com END:VEVENT END:VCALENDAR
### 4.1.2 Changing A Published Event ✏️
The iCalendar object below describes an update to the event described in 4.1.1. The time has been changed, an end time has been added, and the sequence number has been adjusted 🔄.
BEGIN:VCALENDAR METHOD:PUBLISH VERSION:2.0 PRODID:-//ACME/DesktopCalendar//EN BEGIN:VEVENT ORGANIZER:mailto:a@example.com DTSTAMP:19970612T190000Z DTSTART:19970701T210000Z DTEND:19970701T230000Z SEQUENCE:1 UID:0981234-1234234-23@example.com SUMMARY:ST. PAUL SAINTS -VS- DULUTH-SUPERIOR DUKES END:VEVENT END:VCALENDAR
The "UID" property is used by the client to identify the event. The "SEQUENCE" property indicates that this is a change to the event. The event with a matching UID and sequence number 0 is superseded by this event 👀.
The "SEQUENCE" property gives you a reliable way to tell different versions of the same event apart 💖. Each time an event is published, its sequence number is incremented. If a client receives an event with a sequence number 5 and finds it has the same event with sequence number 2, the event SHOULD be updated. However, if the client received an event with sequence number 2 and finds it already has sequence number 5 of the same event, the event MUST NOT be updated 🙅♀️.
### 4.1.3 Canceling A Published Event 🚫
The iCalendar object below cancels the event described in 4.1.1. This cancels the event with a "SEQUENCE" property of 0, 1, and 2 💀.
BEGIN:VCALENDAR METHOD:CANCEL VERSION:2.0 PRODID:-//ACME/DesktopCalendar//EN BEGIN:VEVENT ORGANIZER:mailto:a@example.com COMMENT:DUKES forfeit the game SEQUENCE:2 UID:0981234-1234234-23@example.com DTSTAMP:19970613T190000Z END:VEVENT END:VCALENDAR
### 4.1.4 A Rich Published Event 💎
This example describes the same event as in 4.1.1, but in way more detail 🤩.
BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:PUBLISH SCALE:GREGORIAN VERSION:2.0 BEGIN:VTIMEZONE TZID:America-Chicago TZURL:http://zones.stds_r_us.net/tz/America-Chicago BEGIN:STANDARD DTSTART:19671029T020000 RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10 TZOFFSETFROM:-0500 TZOFFSETTO:-0600 TZNAME:CST END:STANDARD BEGIN:DAYLIGHT DTSTART:19870405T020000 RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4 TZOFFSETFROM:-0600 TZOFFSETTO:-0500 TZNAME:CDT END:DAYLIGHT END:VTIMEZONE BEGIN:VEVENT ORGANIZER:mailto:a@example.com ATTACH:http://www.dukes.com/ CATEGORIES:SPORTS EVENT,ENTERTAINMENT CLASS:PRIVATE DESCRIPTION:MIDWAY STADIUM\n Big time game. MUST see.\n Expected duration:2 hours\n DTEND;TZID=America-Chicago:19970701T180000 DTSTART;TZID=America-Chicago:19970702T160000 DTSTAMP:19970614T190000Z STATUS:CONFIRMED LOCATION;VALUE=URI:http://www.midwaystadium.com/ PRIORITY:2 RESOURCES:SCOREBOARD SEQUENCE:3 SUMMARY:ST. PAUL SAINTS -VS- DULUTH-SUPERIOR DUKES UID:0981234-1234234-23@example.com RELATED-TO:0981234-1234234-14@example.com BEGIN:VALARM TRIGGER:-PT2H ACTION:DISPLAY DESCRIPTION:You should be leaving for the game now. END:VALARM BEGIN:VALARM TRIGGER:-PT30M ACTION:AUDIO END:VALARM END:VEVENT END:VCALENDAR
The "RELATED-TO" field contains the "UID" property of a related calendar event 🔗. The "SEQUENCE" property value of 3 indicates that this event supersedes versions 0, 1, and 2 ✨.
### 4.1.5 Anniversaries or Events attached to entire days 🎉
This example shows how the "value" parameter ties a "VEVENT" to a day rather than a specific time 🥳.
BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:PUBLISH VERSION:2.0 BEGIN:VEVENT ORGANIZER:mailto:a@example.com DTSTAMP:19970614T190000Z UID:0981234-1234234-23@example.com DTSTART;VALUE=DATE:19970714 RRULE:FREQ=YEARLY;INTERVAL=1 SUMMARY: Bastille Day END:VEVENT END:VCALENDAR
## 4.2 Group Event Examples 🫂
Group events are different from published events because they have "Attendees", and there's interaction between the "Attendees" and the "Organizer" about the event 💬. Individual "A" requests a meeting between individuals "A", "B", "C" and "D". Individual "B" confirms attendance to the meeting. Individual "C" declines attendance. Individual "D" tentatively confirms attendance 🙌. The following table illustrates the the message flow between these individuals. A, the CU scheduling the meeting, is referenced as the "Organizer" 📅.
+---------------------------------------------------------------------+
| Action | "Organizer" | Attendee |
### 4.2.1 A Group Event Request
okay so this is the big group invite bestie 🎀 "A" sends a meeting request to "B", "C", and "D". *E* gets a copy too, but *E* isn't expected to show up and doesn't have to reply. This is basically how CUAs can do an "FYI" feature 💅 Look at the `role` parameter: its default is `req-participant` and you don't have to write it out. Here we use `non-participant` to say *E* is a non-attending CU. You don't need the parameter on the other Attendees because `participant` is already the default ✨
BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:REQUEST VERSION:2.0 BEGIN:VEVENT ORGANIZER:Mailto:A@example.com ATTENDEE;ROLE=CHAIR;PARTSTAT=ACCEPTED;CN=BIG A:Mailto:A@example.com ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL;CN=B:Mailto:B@example.com ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL;CN=C:Mailto:C@example.com ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL;CN=Hal:Mailto:D@example.com ATTENDEE;RSVP=FALSE;TYPE=ROOM:conf_Big@example.com ATTENDEE;ROLE=NON-PARTICIPANT;RSVP=FALSE:Mailto:E@example.com DTSTAMP:19970611T190000Z DTSTART:19970701T200000Z DTEND:19970701T2000000Z SUMMARY:Conference UID:calsrv.example.com-873970198738777@example.com SEQUENCE:0 STATUS:CONFIRMED END:VEVENT END:VCALENDAR
### 4.2.2 Reply To A Group Event Request
Attendee "B" says yes to the meeting 🦋
BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:REPLY VERSION:2.0 BEGIN:VEVENT ATTENDEE;PARTSTAT=ACCEPTED:Mailto:B@example.com ORGANIZER:MAILTO:A@example.com UID:calsrv.example.com-873970198738777@example.com SEQUENCE:0 REQUEST-STATUS:2.0;Success DTSTAMP:19970612T190000Z END:VEVENT END:VCALENDAR
<lavender>"B" could have declined or said tentative instead, by setting the `ATTENDEE` `partstat` parameter to `declined` or `tentative`. And `REQUEST-STATUS` is not required in successful transactions 🌸</lavender>
### 4.2.3 Update An Event
The event got moved to a new time ⏰ The `UID` property stays the same and the `SEQUENCE` property gets bumped to 1, and together those two tell everyone this is an update 🫶
BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:REQUEST VERSION:2.0 BEGIN:VEVENT ORGANIZER:Mailto:A@example.com ATTENDEE;ROLE=CHAIR;PARTSTAT=ACCEPTED:Mailto:A@example.com ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:Mailto:B@example.com ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:Mailto:C@example.com ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL;CN=Hal:Mailto:D@example.com ATTENDEE;ROLE=NON-PARTICIPANT;RSVP=FALSE; CUTYPE=ROOM:Mailto:Conf@example.com ATTENDEE;ROLE=NON-PARTICIPANT;RSVP=FALSE:Mailto:E@example.com DTSTART:19970701T180000Z DTEND:19970701T190000Z SUMMARY:Phone Conference UID:calsrv.example.com-873970198738777@example.com SEQUENCE:1 DTSTAMP:19970613T190000Z STATUS:CONFIRMED END:VEVENT END:VCALENDAR
### 4.2.4 Countering an Event Proposal
Okay this one is giving negotiation arc 👑 "A" sends a `REQUEST` to "B" and "C", then "B" comes back with a counter-proposal to change the time and location.
"A" sends the following `REQUEST`:
BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:REQUEST VERSION:2.0 BEGIN:VEVENT ORGANIZER:Mailto:A@example.com ATTENDEE;ROLE=CHAIR;PARTSTAT=ACCEPTED:Mailto:A@example.com ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:Mailto:B@example.com ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:Mailto:C@example.com DTSTART:19970701T190000Z DTEND:19970701T200000Z SUMMARY:Discuss the Merits of the election results LOCATION:Green Conference Room UID:calsrv.example.com-873970198738777a@example.com SEQUENCE:0 DTSTAMP:19970611T190000Z STATUS:CONFIRMED END:VEVENT END:VCALENDAR
"B" sends `COUNTER` to "A" asking for changes to the time and place 🙈 They use the `COMMENT` property to explain why. Also, <red>the `SEQUENCE` property is NOT incremented on a `COUNTER`</red>, so keep that in mind!
BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:COUNTER VERSION:2.0 BEGIN:VEVENT ORGANIZER:Mailto:A@example.com ATTENDEE;ROLE=CHAIR;PARTSTAT=ACCEPTED:Mailto:A@example.com ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:Mailto:B@example.com ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:Mailto:C@example.com DTSTART:19970701T160000Z DTEND:19970701T190000Z DTSTAMP:19970612T190000Z SUMMARY:Discuss the Merits of the election results LOCATION:Green Conference Room COMMENT:This time works much better and I think the big conference room is too big UID:calsrv.example.com-873970198738777a@example.com SEQUENCE:0 DTSTAMP:19970611T190000Z END:VEVENT END:VCALENDAR
"A" accepts "B"'s changes ✨ To accept a counter-proposal, the `Organizer` sends a new `REQUEST` event with an incremented sequence number.
BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:REQUEST VERSION:2.0 BEGIN:VEVENT ORGANIZER:Mailto:A@example.com ATTENDEE;ROLE=CHAIR;PARTSTAT=ACCEPTED:Mailto:A@example.com ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:Mailto:B@example.com ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:Mailto:C@example.com DTSTAMP:19970613T190000Z DTSTART:19970701T160000Z DTEND:19970701T190000Z SUMMARY:Discuss the Merits of the election results - changed to meet B's schedule LOCATION:Green Conference Room UID:calsrv.example.com-873970198738777@example.com SEQUENCE:1 STATUS:CONFIRMED END:VEVENT END:VCALENDAR
Or, if "A" doesn't like it, "A" can reject "B"'s counter proposal instead 💀
BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:DECLINECOUNTER VERSION:2.0 BEGIN:VEVENT ORGANIZER:Mailto:A@example.com ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:Mailto:B@example.com COMMENT:Sorry, I cannot change this meeting time UID:calsrv.example.com-873970198738777@example.com SEQUENCE:0 DTSTAMP:19970614T190000Z END:VEVENT END:VCALENDAR
### 4.2.5 Delegating an Event
Delegation is a whole thing 🧚 When you pass an event request on to another Calendar User, the Delegator has to update the Organizer with a `REPLY` AND send a request to the Delegate. There is currently no protocol limitation on delegation depth, so the original delegate can pass it along to someone else, and so on, and so on 🌈 When a CUA hands a request to another CUA, the Delegator has a few responsibilities. The Delegator MUST:
- Send a `REPLY` to the Organizer with the following updates:
- The Delegator's `ATTENDEE` property `partstat` parameter is set to `delegated`, and the `delegated-to` parameter is set to the address of the Delegate
- Add an extra `ATTENDEE` property for the Delegate, with the `delegated-from` property parameter set to the Delegator
- Say whether they still want updates whenever the Organizer sends out updated versions of the event. Setting the `rsvp` property parameter to `TRUE` causes the updates to be sent, and setting it to `FALSE` means no further updates get sent. Either way, if the Delegate declines the invitation, the Delegator gets notified 🔥
- The Delegator MUST also send a copy of the original `REQUEST` method to the Delegate.
The Delegate doesn't have to include the Delegator in their `REPLY` method. However, it is strongly advised, because it lets the Delegator know whether the Delegate plans to attend the meeting. <lavender>[Editors note: How so?]</lavender> If the Delegate declines the meeting, the Delegator may choose to delegate the `REQUEST` to another CUA. The process is the same 💅
+---------------------------------------------------------------------+
| Action | "Organizer" | Attendee |
+---------------------------------------------------------------------+
| Initiate a meeting | "A" sends a REQUEST | |
|---|---|---|
| request | message to "B" and | |
| "C" |
+---------------------------------------------------------------------+
| Delegate: | "C" sends a REPLY to "A" | |
|---|---|---|
| "C" delegates to | with the ATTENDEE. | |
| "E" | "partstat" parameter set | |
| to "delegated" and with a | ||
| new "ATTENDEE" property | ||
| for "E". "E's" ATTENDEE | ||
| "delegated-from" param | ||
| is set to "C". "C's" | ||
| ATTENDEE "delegated-to" | ||
| param is set to "E". | ||
| "C" sends REQUEST message | ||
| to "E" with the original | ||
| meeting request | ||
| information. The | ||
| "partstat" property | ||
| parameter for "C" is set | ||
| to "delegated" and the | ||
| "delegated-to" | ||
| parameter is set to | ||
| the address of "E". An | ||
| "ATTENDEE" property is | ||
| added for "E" and the | ||
| "delegated-from" | ||
| parameter is set to | ||
| the address of "C". |
+---------------------------------------------------------------------+
+---------------------------------------------------------------------+
| Confirm meeting | "E" sends REPLY message | |
|---|---|---|
| attendance | to "A" and optionally "C" | |
| with its "partstat" | ||
| property parameter set | ||
| to "ACCEPTED" |
+---------------------------------------------------------------------+
| Optional: | "A" sends REQUEST | |
|---|---|---|
| Redistribute | message to "B", "C" | |
| meeting to | and "E". | |
| attendees |
+---------------------------------------------------------------------+
<lavender>okay so this table is the whole story in one glance 👀</lavender> "C" responds to the "Organizer" 💌
BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:REPLY VERSION:2.0 BEGIN:VEVENT ORGANIZER:MAILTO:A@Example.com ATTENDEE;PARTSTAT=DELEGATED;DELEGATED- TO="Mailto:E@example.com":Mailto:C@example.com UID:calsrv.example.com-873970198738777@example.com SEQUENCE:0 REQUEST-STATUS:2.0;Success DTSTAMP:19970611T190000Z END:VEVENT END:VCALENDAR
<pink>Attendee "C" delegates presence at the meeting to "E" 🎀</pink>
BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:REQUEST VERSION:2.0 BEGIN:VEVENT ORGANIZER:Mailto:A@example.com ATTENDEE;PARTSTAT=DELEGATED;DELEGATED- TO="Mailto:E@example.com":Mailto:C@example.com ATTENDEE;RSVP=TRUE; DELEGATED-FROM="Mailto:C@example.com":Mailto:E@example.com DTSTART:19970701T180000Z DTEND:19970701T200000Z SUMMARY:Phone Conference UID:calsrv.example.com-873970198738777@example.com SEQUENCE:0 STATUS:CONFIRMED DTSTAMP:19970611T190000Z END:VEVENT END:VCALENDAR
### 4.2.6 Delegate Accepts the Meeting
To accept a delegated meeting 🧚, the delegate, "E", sends the following message to "A" and "C" 💜
BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:REPLY VERSION:2.0 BEGIN:VEVENT ORGANIZER:MAILTO:A@Example.com ATTENDEE;PARTSTAT=ACCEPTED;DELEGATED- FROM="Mailto:C@example.com":Mailto:E@example.com ATTENDEE;PARTSTAT=DELEGATED; DELEGATED-TO="Mailto:E@example.com":Mailto:C@example.com UID:calsrv.example.com-873970198738777@example.com SEQUENCE:0 REQUEST-STATUS:2.0;Success DTSTAMP:19970614T190000Z END:VEVENT END:VCALENDAR
### 4.2.7 Delegate Declines the Meeting
<peach>This one is a little plot twist 😭</peach> In this example the "Delegate" declines the meeting request and sets the "ATTENDEE" property "partstat" parameter to "DECLINED". The "Organizer" SHOULD resend the "REQUEST" to "C" with the "partstat" parameter of the "Delegate" set to "declined". This lets the "Delegator" know that the "Delegate" has declined and gives the "Delegator" a chance to either accept the request or delegate it to another CU 🦋
Here is the response from "E" to "A" and "C". Notice the "COMMENT" property that "E" uses to explain why the delegation was declined 🙈
BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:REPLY VERSION:2.0 BEGIN:VEVENT ORGANIZER:MAILTO:A@Example.com ATTENDEE;PARTSTAT=DELEGATED; DELEGATED-TO="Mailto:E@example.com":Mailto:C@example.com ATTENDEE;PARTSTAT=DECLINED; DELEGATED-FROM="Mailto:C@example.com":Mailto:E@example.com COMMENT:Sorry, I will be out of town at that time. UID:calsrv.example.com-873970198738777@example.com SEQUENCE:0 REQUEST-STATUS:2.0;Success DTSTAMP:19970614T190000Z END:VEVENT END:VCALENDAR
"A" resends the "REQUEST" method to "C". <mint>"A" can also choose to mention in the "COMMENT" property that the item was delegated 🌸</mint>
BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:REQUEST VERSION:2.0 BEGIN:VEVENT ORGANIZER:MAILTO:A@Example.com ATTENDEE;PARTSTAT=DECLINED; DELEGATED-FROM="Mailto:C@example.com":Mailto:E@example.com ATTENDEE;RSVP=TRUE:Mailto:C@example.com UID:calsrv.example.com-873970198738777@example.com SEQUENCE:0 SUMMARY:Phone Conference DTSTART:19970701T180000Z DTEND:19970701T200000Z DTSTAMP:19970614T200000Z COMMENT:DELEGATE (ATTENDEE Mailto:E@example.com) DECLINED YOUR INVITATION END:VEVENT END:VCALENDAR
### 4.2.8 Forwarding an Event Request
<cyan>Okay, forwarding is giving party crasher 🥳</cyan> The protocol does not prevent an "Attendee" from "forwarding" a "VEVENT" calendar component to other "Calendar Users". Forwarding is different from delegation, though. The forwarded "Calendar User" (often called a "Party Crasher") does NOT replace the forwarding "Calendar User" 💅 Implementations are not required to add the "Party Crasher" to the "Attendee" list, so there is no guarantee that a "Party Crasher" will get more updates to the Event 💀 The forwarding "Calendar User" SHOULD NOT add the "Party Crasher" to the attendee list. The "Organizer" MAY add the forwarded "Calendar User" to the attendee list ✨
### 4.2.9 Cancel A Group Event
<yellow>Main character energy: individual "A" calls a meeting 📅</yellow> Individual "A" requests a meeting between individuals "A", "B", "C", and "D". Individual "B" declines attendance. Individual "A" then decides to cancel the meeting. The table below shows the messages these individuals send back and forth 🍓
Messages related to a previously canceled event ("SEQUENCE" property value is less than the "SEQUENCE" property value of the "CANCEL" message) MUST be ignored. <red>Do not skip this one, bestie 🚫</red>
+--------------------------------------------------------------------+
| Action | "Organizer" | "Attendee" |
+--------------------------------------------------------------------+
| Initiate a meeting | "A" sends a REQUEST | |
|---|---|---|
| request | message to "B", "C", | |
| and "D" |
+--------------------------------------------------------------------+
| Decline the meeting | "B" sends a "REPLY" | |
|---|---|---|
| request | message to "A" with its | |
| "partstat" para- | ||
| set to "declined". |
+--------------------------------------------------------------------+
| Cancel the meeting | "A" sends a CANCEL | |
|---|---|---|
| message to "B", "C" | ||
| and "D" |
+--------------------------------------------------------------------+
Here is how "A" cancels the event 🥀
BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:CANCEL VERSION:2.0 BEGIN:VEVENT ORGANIZER:Mailto:A@example.com ATTENDEE;TYPE=INDIVIDUAL;Mailto:A@example.com ATTENDEE;TYPE=INDIVIDUAL:Mailto:B@example.com ATTENDEE;TYPE=INDIVIDUAL:Mailto:C@example.com ATTENDEE;TYPE=INDIVIDUAL:Mailto:D@example.com COMMENT:Mr. B cannot attend. It's raining. Lets cancel. UID:calsrv.example.com-873970198738777@example.com SEQUENCE:1 STATUS:CANCELLED DTSTAMP:19970613T190000Z END:VEVENT END:VCALENDAR
### 4.2.10 Removing Attendees
<hotpink>Okay, the "B" drama continues 🫣</hotpink> "A" wants to remove "B" from a meeting. This is done by sending a "CANCEL" to "B" and taking "B" off the attendee list in the master copy of the event 💖
+--------------------------------------------------------------------+
| Action | "Organizer" | "Attendee" |
+--------------------------------------------------------------------+
| Remove an "B" | "A" sends a CANCEL | |
|---|---|---|
| as an "Attendee" | message to "B" |
+--------------------------------------------------------------------+
| Update the master | "A" sends the | |
|---|---|---|
| copy of the event | updated event to | |
| the remaining | ||
| "Attendees" |
+--------------------------------------------------------------------+
The original meeting includes "A", "B", "C", and "D". The example below shows the "CANCEL" that "A" sends to "B". Heads up: the "STATUS" property is left out here 👀 That's because this is only used when the whole meeting is cancelled, not when the goal is to remove an "Attendee" from the Event.
BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:CANCEL VERSION:2.0 BEGIN:VEVENT ORGANIZER:Mailto:A@example.com ATTENDEE:mailto:B@example.com COMMENT:You're off the hook for this meeting UID:calsrv.example.com-873970198738777@example.com DTSTAMP:19970613T193000Z SEQUENCE:1 END:VEVENT END:VCALENDAR
Here is the updated master copy of the event. The "Organizer" MAY resend the updated event to the remaining "Attendees". Notice that "B" is gone 🦋
BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:REQUEST VERSION:2.0 BEGIN:VEVENT ORGANIZER:Mailto:A@example.com ATTENDEE;ROLE=CHAIR;PARTSTAT=ACCEPTED:Mailto:A@example.com ATTENDEE;TYPE=INDIVIDUAL:Mailto:C@example.com ATTENDEE;TYPE=INDIVIDUAL:Mailto:D@example.com ATTENDEE;TYPE=ROOM:CR_Big@example.com ATTENDEE;ROLE=NON-PARTICIPANT; RSVP=FALSE:Mailto:E@example.com DTSTAMP:19970611T190000Z DTSTART:19970701T200000Z DTEND:19970701T203000Z SUMMARY:Phone Conference UID:calsrv.example.com-873970198738777@example.com SEQUENCE:2 STATUS:CONFIRMED END:VEVENT END:VCALENDAR
### 4.2.11 Replacing the Organizer
<rainbow>Okay this one is a full telenovela 🌈😭</rainbow> The scenario for this example begins with "A" as the "Organizer" for a recurring meeting with "B", "C", and "D". "A" gets a new job offer in another country and drops out of touch. "A" left no forwarding address and no way to be reached. Using out-of-band communication, the other "Attendees" eventually find out what happened and agree that "B" should become the new "Organizer" for the meeting. So "B" sends out a new version of the event, and the other "Attendees" agree to accept "B" as the new "Organizer". "B" also removes "A" from the event 💅
When the "Organizer" is replaced, the "SEQUENCE" property value MUST be incremented. <peach>Don't forget this part, it's important 🔥</peach>
This is the message "B" sends to "C" and "D" 💌
BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:REQUEST VERSION:2.0 BEGIN:VEVENT ORGANIZER:Mailto:B@example.com ATTENDEE;ROLE=CHAIR;STATUS=ACCEPTED:Mailto:B@example.com ATTENDEE;TYPE=INDIVIDUAL:Mailto:C@example.com ATTENDEE;TYPE=INDIVIDUAL:Mailto:D@example.com DTSTAMP:19970611T190000Z DTSTART:19970701T200000Z DTEND:19970701T203000Z RRULE:FREQ=WEEKLY SUMMARY:Phone Conference UID:123456@example.com SEQUENCE:1 STATUS:CONFIRMED END:VEVENT END:VCALENDAR
## 4.3 Busy Time Examples 🫶
okay so busy time objects can be used in a few different ways 💅 First, a CU can ask another CU for busy time over a specific range of time, and that request can get answered with a busy time Reply 🎀 Or a CU can just publish their busy time for an interval and point other CUs to where it's posted ✨ Both scenarios are covered below 🦋
Individual "A" publishes busy time for one week. 🌸
BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN VERSION:2.0 METHOD:PUBLISH BEGIN:VFREEBUSY DTSTAMP:19980101T124100Z ORGANIZER:MAILTO:A@Example.com DTSTART:19980101T124200Z DTEND:19980107T124200Z FREEBUSY:19980101T180000Z/19980101T190000Z FREEBUSY:19980103T020000Z/19980103T050000Z FREEBUSY:19980107T020000Z/19980107T050000Z FREEBUSY:19980113T000000Z/19980113T010000Z FREEBUSY:19980115T190000Z/19980115T200000Z FREEBUSY:19980115T220000Z/19980115T230000Z FREEBUSY:19980116T013000Z/19980116T043000Z END:VFREEBUSY END:VCALENDAR
Individual "A" requests busy time from individuals "B" and "C", and then "B" and "C" reply to "A" with their busy time data 💖 The table below shows the messages that get passed back and forth between them 🧚
+--------------------------------------------------------------------+
| Action | "Organizer" | Attendee |
+--------------------------------------------------------------------+
| Initiate a busy | "A" sends "REQUEST" | |
|---|---|---|
| time request | message to "B" and | |
| and "C" |
+--------------------------------------------------------------------+
| Reply to the "BUSY" | "B" sends a "REPLY" | |
|---|---|---|
| request with "BUSY" | message to "A" with | |
| time data | busy time data |
+--------------------------------------------------------------------+
### 4.3.1 Request Busy Time 📩
`"A" sends a "BUSY-REQUEST" to "B" and "C" for busy time` 💌
BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:REQUEST VERSION:2.0 BEGIN:VFREEBUSY ORGANIZER:Mailto:A@example.com ATTENDEE;ROLE=CHAIR:Mailto:A@example.com ATTENDEE:Mailto:B@example.com ATTENDEE:Mailto:C@example.com DTSTAMP:19970613T190000Z DTSTART:19970701T080000Z DTEND:19970701T200000 UID:calsrv.example.com-873970198738777@example.com END:VFREEBUSY END:VCALENDAR
### 4.3.2 Reply To A Busy Time Request 🔥
`"B" sends a "REPLY" method type of a "VFREEBUSY" calendar component to "A"` 💅
BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:REPLY VERSION:2.0 BEGIN:VFREEBUSY ORGANIZER:MAILTO:A@example.com ATTENDEE:Mailto:B@example.com DTSTART:19970701T080000Z DTEND:19970701T200000Z UID:calsrv.example.com-873970198738777@example.com FREEBUSY:19970701T090000Z/PT1H,19970701T140000Z/PT30M DTSTAMP:19970613T190030Z END:VFREEBUSY END:VCALENDAR
So "B" is busy from 09:00 to 10:00 and from 14:00 to 14:30 😭🫶
---
## 4.4 Recurring Event and Time Zone Examples 🌈
### 4.4.1 A Recurring Event Spanning Time Zones 🌍
This event is a weekly phone conference, and the "Attendees" are each in a different time zone 🍓
BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:REQUEST VERSION:2.0 BEGIN:VTIMEZONE TZID:America-SanJose TZURL:http://zones.stds_r_us.net/tz/America-SanJose BEGIN:STANDARD DTSTART:19671029T020000 RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10 TZOFFSETFROM:-0700 TZOFFSETTO:-0800 TZNAME:PST END:STANDARD BEGIN:DAYLIGHT DTSTART:19870405T020000 RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4 TZOFFSETFROM:-0800 TZOFFSETTO:-0700 TZNAME:PDT END:DAYLIGHT END:VTIMEZONE BEGIN:VEVENT ORGANIZER:Mailto:A@example.com ATTENDEE;ROLE=CHAIR;PARTSTAT=ACCEPTED;TYPE=INDIVIDUAL:A@example.COM ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:B@example.fr ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:c@example.jp DTSTAMP:19970613T190030Z DTSTART;TZID=America-SanJose:19970701T140000 DTEND;TZID=America-SanJose:19970701T150000 RRULE:FREQ=WEEKLY;INTERVAL=20;WKST=SU;BYDAY=TU RDATE;TZID=America-SanJose:19970910T140000 EXDATE;TZID=America-SanJose:19970909T140000 EXDATE;TZID=America-SanJose:19971028T140000 SUMMARY:Weekly Phone Conference UID:calsrv.example.com-873970198738777@example.com SEQUENCE:0 STATUS:CONFIRMED END:VEVENT END:VCALENDAR
The first two components in this iCalendar object are the time zone components 🕰️ The "DTSTART" date lines up with the first instance of the RRULE property ✨
The recurring meeting is set in one particular time zone, probably the originator's 💜 Each "Attendee"'s client is in charge of working out when the recurrence lands in that "Attendee's" own time zone 🫶
Okay, the repeating event starts on Tuesday, July 1, 1997 at 2:00pm PDT 💖 "Attendee" B@example.fr is in France, where local time on that date is 9 hours ahead of PDT, so it's 23:00 there 🥐 "Attendee" C@example.jp is in Japan, where local time is 8 hours ahead of UTC, so it's Wednesday, July 2 at 06:00 🍣 The event repeats weekly on Tuesdays (in PST/PDT), and the "RRULE" property gives us 20 instances total 🔁 The last instance falls on Tuesday, November 11, 1997 at 2:00pm PDT 🥹 The "RDATE" property adds one more instance: WED, 10-SEP-1997 2:00 PM PST 🎀
There are two exceptions to this recurring appointment. The first one is:
TUE, 09-SEP-1997 23:00 GMT TUE, 09-SEP-1997 14:00 PDT WED, 10-SEP-1997 06:00 JST
and the second one is:
TUE, 28-OCT-1997 23:00 GMT TUE, 28-OCT-1997 14:00 PST WED, 29-OCT-1997 06:00 JST
### 4.4.2 Modify A Recurring Instance ✏️
In this example, the "Organizer" sets up a recurring meeting 💌 Later on, the "Organizer" changes one instance of the event by tweaking its "DTSTART" property 🦋 Heads up to notice the "RECURRENCE-ID" property and the "SEQUENCE" property in the second request 👀
**Original Request:**
BEGIN:VCALENDAR METHOD:REQUEST PRODID:-//RDU Software//NONSGML HandCal//EN VERSION:2.0 BEGIN:VEVENT UID:guid-1@host1.com SEQUENCE:0 RRULE:FREQ=MONTHLY;BYMONTHDAY=1;UNTIL=19980901T210000Z ORGANIZER:Mailto:A@example.com ATTENDEE;ROLE=CHAIR;PARTSTAT=ACCEPTED:Mailto:A@example.com ATTENDEE:Mailto:B@example.com ATTENDEE:Mailto:C@example.com ATTENDEE:Mailto:D@example.com DESCRIPTION:IETF-C&S Conference Call CLASS:PUBLIC SUMMARY:IETF Calendaring Working Group Meeting DTSTART:19970601T210000Z DTEND:19970601T220000Z LOCATION:Conference Call DTSTAMP:19970526T083000Z STATUS:CONFIRMED END:VEVENT END:VCALENDAR
This event request changes the time of one specific instance 🌸 It moves the July 1st instance over to July 3rd 🎀
BEGIN:VCALENDAR METHOD:REQUEST PRODID:-//RDU Software//NONSGML HandCal//EN VERSION:2.0 BEGIN:VEVENT UID:guid-1@host1com RECURRENCE-ID:19970701T210000Z SEQUENCE:1 ORGANIZER:Mailto:A@example.com ATTENDEE;ROLE=CHAIR;PARTSTAT=ACCEPTED:Mailto:A@example.com ATTENDEE:Mailto:B@example.com ATTENDEE:Mailto:C@example.com ATTENDEE:Mailto:D@example.com DESCRIPTION:IETF-C&S Conference Call CLASS:PUBLIC SUMMARY:IETF Calendaring Working Group Meeting DTSTART:19970703T210000Z DTEND:19970703T220000Z LOCATION:Conference Call DTSTAMP:19970626T093000Z STATUS:CONFIRMED END:VEVENT END:VCALENDAR
### 4.4.3 Cancel an Instance 🙅♀️
In this example, the "Organizer" of a recurring event deletes the August 1st instance 💀
BEGIN:VCALENDAR METHOD:CANCEL PRODID:-//RDU Software//NONSGML HandCal//EN VERSION:2.0 BEGIN:VEVENT UID:guid-1@host1.com ORGANIZER:Mailto:A@example.com ATTENDEE;ROLE=CHAIR;PARTSTAT=ACCEPTED:Mailto:A@example.com ATTENDEE:Mailto:B@example.com ATTENDEE:Mailto:C@example.com ATTENDEE:Mailto:D@example.com RECURRENCE-ID:19970801T210000Z SEQUENCE:2 STATUS:CANCELLED DTSTAMP:19970721T093000Z END:VEVENT END:VCALENDAR
### 4.4.4 Cancel Recurring Event 🗑️
In this example, the "Organizer" wants to cancel the whole recurring event, along with any exceptions 🥀
BEGIN:VCALENDAR METHOD:CANCEL PRODID:-//RDU Software//NONSGML HandCal//EN VERSION:2.0 BEGIN:VEVENT UID:guid-1@host1.com ORGANIZER:Mailto:A@example.com ATTENDEE;ROLE=CHAIR;PARTSTAT=ACCEPTED:Mailto:A@example.com ATTENDEE:Mailto:B@example.com ATTENDEE:Mailto:C@example.com ATTENDEE:Mailto:D@example.com DTSTAMP:19970721T103000Z STATUS:CANCELLED SEQUENCE:3 END:VEVENT END:VCALENDAR
### 4.4.5 Change All Future Instances 🗺️
This example moves the meeting location from a conference call to Seattle, starting September 1 and carrying on to every future instance 🌲
BEGIN:VCALENDAR METHOD:REQUEST PRODID:-//RDU Software//NONSGML HandCal//EN VERSION:2.0 BEGIN:VEVENT UID:guid-1@host1.com RECURRENCE-ID;THISANDFUTURE:19970901T210000Z SEQUENCE:3 ORGANIZER:Mailto:A@example.com ATTENDEE;ROLE=CHAIR;PARTSTAT=ACCEPTED:Mailto:A@example.com ATTENDEE;RSVP=TRUE:Mailto:B@example.com ATTENDEE;RSVP=TRUE:Mailto:C@example.com ATTENDEE;RSVP=TRUE:Mailto:D@example.com DESCRIPTION:IETF-C&S Discussion CLASS:PUBLIC SUMMARY:IETF Calendaring Working Group Meeting DTSTART:19970901T210000Z DTEND:19970901T220000Z LOCATION:Building 32, Microsoft, Seattle, WA DTSTAMP:19970526T083000Z STATUS:CONFIRMED END:VEVENT END:VCALENDAR
### 4.4.6 Add A New Instance To A Recurring Event ➕
This example adds a one-time extra instance to the recurring event 🧁 The "Organizer" adds a second July meeting on the 15th 🎉
BEGIN:VCALENDAR METHOD:ADD PRODID:-//RDU Software//NONSGML HandCal//EN VERSION:2.0 BEGIN:VEVENT UID:123456789@host1.com SEQUENCE:4 ORGANIZER:Mailto:A@example.com ATTENDEE;ROLE=CHAIR;PARTSTAT=ACCEPTED:Mailto:A@example.com ATTENDEE;RSVP=TRUE:Mailto:B@example.com ATTENDEE;RSVP=TRUE:Mailto:C@example.com ATTENDEE;RSVP=TRUE:Mailto:D@example.com DESCRIPTION:IETF-C&S Conference Call CLASS:PUBLIC SUMMARY:IETF Calendaring Working Group Meeting DTSTART:19970715T210000Z DTEND:19970715T220000Z LOCATION:Conference Call DTSTAMP:19970629T093000Z STATUS:CONFIRMED END:VEVENT END:VCALENDAR
### 4.4.7 Add A New Series Of Instances To A Recurring Event
okay so bestie, picture this: a meeting that's been on repeat every Tuesday 📅. The "Organizer" is like "actually we need Tuesdays AND Thursdays now" 💅 but doesn't want to reschedule the whole thing or lose any of the per-instance info that's already been collected 🥺. Main character energy of a scheduler, honestly 👑.
The original event:
BEGIN:VCALENDAR METHOD:REQUEST PRODID:-//RDU Software//NONSGML HandCal//EN VERSION:2.0 BEGIN:VEVENT UID:123456789@host1.com SEQUENCE:0 RRULE:WKST=SU;BYDAY=TU;FREQ=WEEKLY ORGANIZER:Mailto:A@example.com ATTENDEE;ROLE=CHAIR;PARTSTAT=ACCEPTED:Mailto:A@example.com ATTENDEE;RSVP=TRUE:Mailto:B@example.com SUMMARY:Review Accounts DTSTART:19980303T210000Z DTEND:19980303T220000Z LOCATION:The White Room DTSTAMP:19980301T093000Z STATUS:CONFIRMED END:VEVENT END:VCALENDAR
Okay, so assume a ton of other updates have happened to this event and there's a lot of instance-specific stuff hanging out in the recurring series 🧚. The "SEQUENCE" property value is 7 for the next update. Now the "Organizer" wants to add Thursdays to the event 🍓:
BEGIN:VCALENDAR METHOD:ADD PRODID:-//RDU Software//NONSGML HandCal//EN VERSION:2.0 BEGIN:VEVENT UID:123456789@host1.com SEQUENCE:7 RRULE:WKST=SU;BYDAY=TH;FREQ=WEEKLY ORGANIZER:Mailto:A@example.com ATTENDEE;ROLE=CHAIR;PARTSTAT=ACCEPTED:Mailto:A@example.com ATTENDEE;RSVP=TRUE:Mailto:B@example.com SUMMARY:Review Accounts DTSTART:19980303T210000Z DTEND:19980303T220000Z DTSTAMP:19980303T193000Z LOCATION:The Usual conference room STATUS:CONFIRMED END:VEVENT END:VCALENDAR
Alternatively, if the "Organizer" isn't worried about per-instance updates, the whole event can be rescheduled with a "REQUEST" 🔄. You do this by using the "UID" of the event you're rescheduling and including the modified "RRULE". Just know that since this is a full reschedule, any instance-specific info will be lost 💀.
BEGIN:VCALENDAR METHOD:REQUEST PRODID:-//RDU Software//NONSGML HandCal//EN VERSION:2.0 BEGIN:VEVENT UID:123456789@host1.com SEQUENCE:7 RRULE:WKST=SU;BYDAY=TU,TH;FREQ=WEEKLY ORGANIZER:Mailto:A@example.com ATTENDEE;ROLE=CHAIR;PARTSTAT=ACCEPTED:Mailto:A@example.com ATTENDEE;RSVP=TRUE:Mailto:B@example.com SUMMARY:Review Accounts DTSTART:19980303T210000Z DTEND:19980303T220000Z DTSTAMP:19980303T193000Z LOCATION:The White Room STATUS:CONFIRMED END:VEVENT END:VCALENDAR
The next few examples show how an "Organizer" responds to a "REFRESH" sent by an "Attendee" after a bunch of instance-specific changes 🦋. To convey all of those instance changes, the "Organizer" must provide the latest event description and the relevant instances. The first three examples show the history, starting with the initial "VEVENT" request, then the instance changes, and finally the "REFRESH" itself ✨.
**Original Request:**
BEGIN:VCALENDAR METHOD:REQUEST PRODID:-//RDU Software//NONSGML HandCal//EN VERSION:2.0 BEGIN:VEVENT UID:123456789@host1.com SEQUENCE:0 RDATE:19980304T180000Z RDATE:19980311T180000Z RDATE:19980318T180000Z ORGANIZER:Mailto:A@example.com ATTENDEE;ROLE=CHAIR;PARTSTAT=ACCEPTED:Mailto:A@example.com ATTENDEE;RSVP=TRUE:Mailto:B@example.com SUMMARY:Review Accounts DTSTART:19980304T180000Z DTEND:19980304T200000Z DTSTAMP:19980303T193000Z LOCATION:Conference Room A STATUS:CONFIRMED END:VEVENT END:VCALENDAR
**The Organizer changes the 2nd instance's Location and Time:**
BEGIN:VCALENDAR METHOD:REQUEST PRODID:-//RDU Software//NONSGML HandCal//EN VERSION:2.0 BEGIN:VEVENT UID:123456789@host1.com SEQUENCE:1 RECURRENCE-ID:19980311T180000Z ORGANIZER:Mailto:A@example.com ATTENDEE;ROLE=CHAIR;PARTSTAT=ACCEPTED:Mailto:A@example.com ATTENDEE;RSVP=TRUE:Mailto:B@example.com SUMMARY:Review Accounts DTSTART:19980311T160000Z DTEND:19980311T180000Z DTSTAMP:19980306T193000Z LOCATION:The Small conference room STATUS:CONFIRMED END:VEVENT END:VCALENDAR
**The Organizer adds a 4th instance of the meeting using the "ADD" method:**
BEGIN:VCALENDAR METHOD:ADD PRODID:-//RDU Software//NONSGML HandCal//EN VERSION:2.0 BEGIN:VEVENT UID:123456789@host1.com SEQUENCE:2 ORGANIZER:Mailto:A@example.com ATTENDEE;ROLE=CHAIR;PARTSTAT=ACCEPTED:Mailto:A@example.com ATTENDEE;RSVP=TRUE:Mailto:B@example.com SUMMARY:Review Accounts DTSTART:19980315T180000Z DTEND:19980315T200000Z DTSTAMP:19980307T193000Z LOCATION:Conference Room A STATUS:CONFIRMED END:VEVENT END:VCALENDAR
If "B" sends a "REFRESH" request, "A" replies with the following to capture all of the instance-specific data 🫶. In this case, the initial request and an additional "VEVENT" that spells out the instance-specific data are both included. Because they're both the same type (they're both "VEVENTS"), they can be packed into the same iCalendar object 🎀.
BEGIN:VCALENDAR METHOD:REQUEST PRODID:-//RDU Software//NONSGML HandCal//EN VERSION:2.0 BEGIN:VEVENT UID:123456789@host1.com SEQUENCE:2 RDATE:19980304T180000Z RDATE:19980311T160000Z RDATE:19980315T180000Z Error! Bookmark not defined. ORGANIZER:Mailto:A@example.com ATTENDEE;ROLE=CHAIR;PARTSTAT=ACCEPTED:Mailto:A@example.com ATTENDEE;RSVP=TRUE:Mailto:B@example.com SUMMARY:Review Accounts DTSTART:19980304T180000Z DTEND:19980304T200000Z DTSTAMP:19980303T193000Z LOCATION:Conference Room A STATUS:CONFIRMED END:VEVENT
BEGIN:VEVENT Error! Bookmark not defined. SEQUENCE:2 RECURRENCE-ID:19980311T160000Z Error! Bookmark not defined. ATTENDEE;ROLE=CHAIR;Error! Bookmark not defined. ATTENDEE;Error! Bookmark not defined. SUMMARY:Review Accounts DTSTART:19980311T160000Z DTEND:19980304T180000Z DTSTAMP:19980306T193000Z LOCATION:The Small conference room STATUS:CONFIRMED END:VEVENT
END:VCALENDAR
### 4.4.8 Counter An Instance Of A Recurring Event
in this one, an "Attendee" counters the "DTSTART" of the proposed second July meeting 🙈. Someone's got a conflict and wants to bump it by an hour, lol relatable 😭.
BEGIN:VCALENDAR METHOD:COUNTER PRODID:-//RDU Software//NONSGML HandCal//EN VERSION:2.0 BEGIN:VEVENT UID:guid-1@host1.com RECURRENCE-ID:19970715T210000Z SEQUENCE:4 ORGANIZER:Mailto:A@example.com ATTENDEE;ROLE=CHAIR;RSVP=TRUE:Mailto:A@example.com ATTENDEE;RSVP=TRUE:Mailto:B@example.com ATTENDEE;RSVP=TRUE:Mailto:C@example.com ATTENDEE;RSVP=TRUE:Mailto:D@example.com DESCRIPTION:IETF-C&S Conference Call CLASS:PUBLIC SUMMARY:IETF Calendaring Working Group Meeting DTSTART:19970715T220000Z DTEND:19970715T230000Z LOCATION:Conference Call COMMENT:May we bump this by an hour? I have a conflict DTSTAMP:19970629T094000Z END:VEVENT END:VCALENDAR
### 4.4.9 Error Reply To A Request
this example is all about a meeting that gets proposed with an unsupported property AND a bad property 🫠. Messy, but very educational 🤓.
**Original Request**
BEGIN:VCALENDAR METHOD:REQUEST PRODID:-//RDU Software//NONSGML HandCal//EN VERSION:2.0 BEGIN:VEVENT UID:guid-1@host1.com SEQUENCE:0 RRULE:FREQ=MONTHLY;BYMONTHDAY=1 ORGANIZER:Mailto:A@example.com ATTENDEE;ROLE=CHAIR:Mailto:A@example.com ATTENDEE;RSVP=TRUE:Mailto:B@example.com ATTENDEE;RSVP=TRUE:Mailto:C@example.com ATTENDEE;RSVP=TRUE:Mailto:D@example.com DESCRIPTION:IETF-C&S Conference Call CLASS:PUBLIC SUMMARY:IETF Calendaring Working Group Meeting DTSTART:19970601T210000Z DTEND:19970601T220000Z DTSTAMP:19970602T094000Z LOCATION:Conference Call STATUS:CONFIRMED FOO:BAR END:VEVENT END:VCALENDAR
**Response from "B" to say that RRULE isn't supported and an unrecognized property was found:**
BEGIN:VCALENDAR PRODID:-//RDU Software//NONSGML HandCal//EN METHOD:REPLY VERSION:2.0 BEGIN:VEVENT ORGANIZER:Mailto:A@example.com ATTENDEE:Mailto:B@example.com REQUEST-STATUS:2.8;Repeating event ignored. Scheduled as a single event;RRULE REQUEST-STATUS:3.0;Invalid Property Name;FOO UID:guid-1@host1.com SEQUENCE:0 DTSTAMP:19970603T094000Z END:VEVENT END:VCALENDAR
## 4.5 Group To-do Examples
this one's a group to-do vibe 📝. Individual "A" creates a group task that "A", "B", "C" and "D" will all take part in. "B" confirms they're in ✅, "C" declines 💔, and "D" tentatively accepts 🤞. The table below shows the exact messages going back and forth. After that, "A" sends a "REQUEST" to get the status of the to-do from each participant, and each response shows that Attendee's completion status 🌈.
+--------------------------------------------------------------------+
| Action | "Organizer" | Attendee |
+--------------------------------------------------------------------+
| Initiate a to-do | "A" sends a REQUEST | |
|---|---|---|
| request | message to "B", "C", | |
| and "D" |
+--------------------------------------------------------------------+
| Accept the to-do | "B" sends a "REPLY" | |
|---|---|---|
| request | message to "A" with its | |
| "partstat" paramater | ||
| set to "accepted". |
+--------------------------------------------------------------------+
| Decline the to-do | "C" sends a REPLY | |
|---|---|---|
| request | message to "A" with its | |
| "partstat" parameter | ||
| set to "declined". |
+--------------------------------------------------------------------+
| Tentatively accept | "D" sends a REPLY | |
|---|---|---|
| the to-do request | message to "A" with its | |
| "partstat" parameter | ||
| set to "tentative". |
+--------------------------------------------------------------------+
| Check attendee | "A" sends a REQUEST | |
|---|---|---|
| completion status | message to "B" and | |
| "D" with current | ||
| information. |
+--------------------------------------------------------------------+
| Attendee indicates | "B" sends a "REPLY" | |
|---|---|---|
| percent complete | message indicating | |
| percent complete |
+--------------------------------------------------------------------+
| Attendee indicates | "D" sends a "REPLY" | |
|---|---|---|
| completion | message indicating | |
| completion |
+--------------------------------------------------------------------+
### 4.5.1 A VTODO Request 📝
okay bestie, this is a sample "REQUEST" for a "VTODO" calendar component that "A" sends to "B", "C", and "D" 💖
BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:REQUEST VERSION:2.0 BEGIN:VTODO ORGANIZER:Mailto:A@example.com ATTENDEE;ROLE=CHAIR:Mailto:A@example.com ATTENDEE;RSVP=TRUE:Mailto:B@example.com ATTENDEE;RSVP=TRUE:Mailto:C@example.com ATTENDEE;RSVP=TRUE:Mailto:D@example.com DTSTART:19970701T170000Z DUE:19970722T170000Z PRIORITY:1 SUMMARY:Create the requirements document UID:calsrv.example.com-873970198738777-00@example.com SEQUENCE:0 DTSTAMP:19970717T200000Z STATUS:Needs Action END:VTODO END:VCALENDAR
### 4.5.2 A VTODO Reply 🎀
"B" accepts the to-do, yay 🥳
BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:REPLY VERSION:2.0 BEGIN:VTODO ORGANIZER:Mailto:A@example.com ATTENDEE;PARTSTAT=ACCEPTED:Mailto:B@example.com UID:calsrv.example.com-873970198738777-00@example.com COMMENT:I'll send you my input by e-mail SEQUENCE:0 DTSTAMP:19970717T203000Z REQUEST-STATUS:2.0;Success END:VTODO END:VCALENDAR
"B" could have declined the TODO or indicated tentative acceptance by setting the `partstat` property parameter to `declined` or `tentative`, respectively. So many options, it's giving choice 🌸
### 4.5.3 A VTODO Request for Updated Status 📣
"A" is asking for status from all "Attendees" 👀
BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:REQUEST VERSION:2.0 BEGIN:VTODO ORGANIZER:Mailto:A@example.com ATTENDEE;ROLE=CHAIR:Mailto:A@example.com ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:Mailto:B@example.com ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:Mailto:D@example.com UID:calsrv.example.com-873970198738777-00@example.com SUMMARY:Create the requirements document PRIORITY:1 SEQUENCE:0 STATUS:IN-PROCESS DTSTART:19970701T170000Z DTSTAMP:19970717T230000Z END:VTODO END:VCALENDAR
### 4.5.4 A Reply: Percent-Complete 📊
this reply says what task is being worked on and that "B" is 75% complete with "B's" part of the assignment 🔥
BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:REPLY VERSION:2.0 BEGIN:VTODO ORGANIZER:MAILTO:A@example.com ATTENDEE;PARTSTAT=IN-PROCESS:Mailto:B@example.com PERCENT-COMPLETE:75 UID:calsrv.example.com-873970198738777-00@example.com DTSTAMP:19970717T233000Z SEQUENCE:0 END:VTODO END:VCALENDAR
### 4.5.5 A Reply: Completed ✅
"D" finished "D's" part of the assignment, literally iconic 👑
BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:REPLY VERSION:2.0 BEGIN:VTODO ORGANIZER:MAILTO:A@example.com ATTENDEE;PARTSTAT=COMPLETED:Mailto:D@example.com UID:calsrv.example.com-873970198738777-00@example.com DTSTAMP:19970717T233000Z SEQUENCE:0 END:VTODO END:VCALENDAR
### 4.5.6 An Updated VTODO Request 🔄
organizer "A" resends the "VTODO" calendar component, and "A" sets the overall completion for the to-do at 40% 💅
BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:REQUEST VERSION:2.0 BEGIN:VTODO ORGANIZER:Mailto:A@example.com ATTENDEE;ROLE=CHAIR;PARTSTAT=ACCEPTED:Mailto:A@example.com ATTENDEE;PARTSTAT=ACCEPTED;TYPE=INDIVIDUAL:Mailto:B@example.com ATTENDEE;PARTSTAT=IN-PROCESS;TYPE=INDIVIDUAL:Mailto:D@example.com DTSTART:19970701T170000Z DUE:19970722T170000Z PRIORITY:1 SUMMARY:Create the requirements document UID:calsrv.example.com-873970198738777-00@example.com SEQUENCE:1 DTSTAMP:19970718T100000Z STATUS:IN-PROGRESS PERCENT-COMPLETE:40 END:VTODO END:VCALENDAR
### 4.5.7 Recurring VTODOs 🔁
the next few examples are all about recurring "VTODO" calendar components, so buckle up 🎢
### 4.5.7.1 Request for a Recurring VTODO 🗓️
in this one "A" sends a recurring "VTODO" calendar component to "B" and "D" 🦋
BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:REQUEST VERSION:2.0 BEGIN:VTODO ORGANIZER:Mailto:A@example.com ATTENDEE;ROLE=CHAIR:Mailto:A@example.com ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:Mailto:B@example.com ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:Mailto:D@example.com RRULE:FREQ=MONTHLY;COUNT=10;BYDAY=1FR DTSTART:19980101T100000-0700 DUE:19980103T100000-0700 SUMMARY:Send Status Reports to Area Managers UID:calsrv.example.com-873970198738777-00@example.com SEQUENCE:0 DTSTAMP:19970717T200000Z STATUS:NEEDS ACTION PRIORITY:1 END:VTODO END:VCALENDAR
### 4.5.7.2 Calculating due dates in recurring VTODOs 🧮
okay so the due date in a recurring "VTODO" calendar component is either a fixed interval specified in the "REQUEST" method, or it's specified using the "RECURRENCE-ID" property. The former is calculated by taking the difference between the "DTSTART" and "DUE" properties and applying it to the start of each recurring instance. Hence, if the initial "VTODO" calendar component has a "DTSTART" property value of `19970701T190000Z` and a "DUE" property value of `19970801T190000Z`, the interval of one day is applied to each recurring instance of the "VTODO" calendar component to work out the "DUE" date of that instance. the math is mathing 🤓✨
### 4.5.7.3 Replying to an instance of a recurring VTODO 💬
in this example "B" gives "A" an update on a single instance of the "VTODO" calendar component 🫶
BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:REPLY VERSION:2.0 BEGIN:VTODO ATTENDEE;PARTSTAT=IN-PROCESS:Mailto:B@example.com PERCENT-COMPLETE:75 UID:calsrv.example.com-873970198738777-00@example.com DTSTAMP:19970717T233000Z RECURRENCE-ID:19980101T170000Z SEQUENCE:1 END:VTODO END:VCALENDAR
## 4.6 Journal Examples 📓
the iCalendar object below describes a single journal entry for October 2, 1997. The "RELATED-TO" property points at the phone conference event that the minutes were taken for 🎀
BEGIN:VCALENDAR METHOD:PUBLISH PRODID:-//ACME/DesktopCalendar//EN VERSION:2.0 BEGIN:VJOURNAL DTSTART:19971002T200000Z ORGANIZER:MAILTO:A@Example.com SUMMARY:Phone conference minutes DESCRIPTION:The editors meeting was held on October 1, 1997. Details are in the attached document. UID:0981234-1234234-2410@example.com RELATED-TO:0981234-1234234-2402-35@example.com ATTACH:ftp://ftp.example.com/pub/ed/minutes100197.txt END:VJOURNAL END:VCALENDAR
## 4.7 Other Examples 🌸
### 4.7.1 Event Refresh 🔄
refresh the event with the "UID" property value of `guid-1-12345@host1.com` 💜
BEGIN:VCALENDAR PRODID:-//RDU Software//NONSGML HandCal//EN METHOD:REFRESH VERSION:2.0 BEGIN:VEVENT ORGANIZER:Mailto:A@example.com ATTENDEE;ROLE=CHAIR;PARTSTAT=ACCEPTED:Mailto:A@example.com ATTENDEE:Mailto:B@example.com ATTENDEE:Mailto:C@example.com ATTENDEE:Mailto:D@example.com UID: guid-1-12345@host1.com DTSTAMP:19970603T094000 END:VEVENT END:VCALENDAR
### 4.7.2 Bad RECURRENCE-ID 🙈
okay, this one's a lil drama 😭 component instances are identified by the combination of "UID", "RECURRENCE-ID", and "SEQUENCE". When an "Organizer" sends a request to an "Attendee", there are three cases where an instance can't be found:
1. The component with the referenced "UID" and "RECURRENCE-ID" has been found, but the "SEQUENCE" number in the calendar store does not match that of the ITIP message.
2. The component with the referenced "UID" has been found and the "SEQUENCE" numbers match, but the "RECURRENCE-ID" can't be found.
3. The "UID" and "SEQUENCE" numbers are found, but the CUA does not support recurrences.
in case (1), two things can happen. If the "SEQUENCE" number of the "Attendee's" instance is larger than the one in the "Organizer's" message, then the "Attendee" is getting an out-of-sequence message and MUST ignore it 🚫. If the "SEQUENCE" number of the "Attendee's" instance is smaller, then the "Organizer" is sending out a newer version of the component, and the "Attendee's" version needs to be updated. Since one or more updates have been missed, the "Attendee" SHOULD send a "REFRESH" message to the "Organizer" to get an updated version of the event 🫠
in case (2), something has gone wrong 💀 Both the "Organizer" and the "Attendee" should have the same instances, but the "Attendee" doesn't have the referenced instance. In this case the "Attendee" SHOULD send a "REFRESH" to the "Organizer" to get an updated version of the event.
in case (3), the limits of the "Attendee's" CUA make it impossible to match any instance other than the single instance scheduled. In this case, the "Attendee" need not send a "REFRESH" to the "Organizer" 🌈
the example below shows a sequence where an "Attendee" sends a "REFRESH" to the "Organizer" 👇
+--------------------------------------------------------------------+
| Action | "Organizer" | Attendee |
+--------------------------------------------------------------------+
| Update an instance | "A" sends "REQUEST" | |
|---|---|---|
| request | message to "B" |
+--------------------------------------------------------------------+
| Attendee requests | "B" sends a "REFRESH" | |
|---|---|---|
| refresh because | message to "A" | |
| "RECURRENCE-ID" was | ||
| not found |
+--------------------------------------------------------------------+
| Refresh the entire | "A" sends the | |
|---|---|---|
| Event | latest copy of the | |
| Event to "B" |
+--------------------------------------------------------------------+
| Attendee handles | "B" updates to the | |
|---|---|---|
| the request and | latest copy of the | |
| updates the | meeting. | |
| instance |
+--------------------------------------------------------------------+
Request from "A":
BEGIN:VCALENDAR METHOD:REQUEST PRODID:-//RDU Software//NONSGML HandCal//EN VERSION:2.0 BEGIN:VEVENT UID:acme-12345@host1.com SEQUENCE:3 RRULE:FREQ=WEEKLY RDATE;VALUE=PERIOD:19970819T210000Z/199700819T220000Z ORGANIZER:Mailto:A@example.com ATTENDEE;ROLE=CHAIR;PARTSTAT=ACCEPTED:Mailto:A@example.com ATTENDEE:Mailto:B@example.com DESCRIPTION:IETF-C&S Conference Call SUMMARY:IETF Calendaring Working Group Meeting DTSTART:19970801T210000Z DTEND:19970801T220000Z RECURRENCE-ID:19970809T210000Z DTSTAMP:19970726T083000 STATUS:CONFIRMED END:VEVENT END:VCALENDAR
"B" has the event with the "UID" property `acme-12345@host1.com`, but "B's" "SEQUENCE" property value is "1" and the event doesn't have an instance at the specified recurrence time. This means "B" has missed at least one update and needs a new copy of the event. "B" asks for the latest copy of the event with this refresh message 🙏
BEGIN:VCALENDAR PRODID:-//RDU Software//NONSGML HandCal//EN METHOD:REFRESH VERSION:2.0 BEGIN:VEVENT ORGANIZER:Mailto:A@example.com ATTENDEE:Mailto:B@example.com UID:acme-12345@host1.com DTSTAMP:19970603T094000 END:VEVENT END:VCALENDAR
# 5 Application Protocol Fallbacks 🌈
## 5.1 Partial Implementation 🦋
applications that support this memo are not required to support the entire protocol, no pressure 🫶 The following describes how methods and properties SHOULD "fallback" in applications that don't support the complete protocol. If a method or property isn't addressed in this section, it may be ignored 💅
### 5.1.1 Event-Related Fallbacks 💅✨
Okay bestie, here's what happens when your app doesn't support every method or property 🫶 Start with the event-related methods:
Method Fallback
PUBLISH Required REQUEST PUBLISH REPLY Required ADD Required CANCEL Required REFRESH Required COUNTER Reply with Not Supported DECLINECOUNTER Required if EVENT-COUNTER is implemented; otherwise reply with Not Supported
Next, the iCalendar-level properties 🌸
iCalendar Property Fallback
CALSCALE Ignore; assume GREGORIAN PRODID Ignore METHOD Required as described in the Method list above VERSION Ignore
Now the event-related components 🦋
Event-Related Components Fallback
VALARM Reply with Not Supported VTIMEZONE Required if any DateTime value refers to a time zone.
And finally the component properties, which is the longest list, so get your snacks 🍓
Component Property Fallback
ATTACH Ignore ATTENDEE Required if EVENT-REQUEST is not implemented; otherwise reply with Not Supported CATEGORIES Ignore CLASS Ignore COMMENT Ignore COMPLETED Ignore nCONTACT Ignore CREATED Ignore DESCRIPTION Required DURATION Reply with Not Supported DTSTAMP Required DTSTART Required DTEND Required EXDATE Ignore EXRULE Ignore Reply with Not Supported. If implemented, VTIMEZONE MUST also be implemented. GEO Ignore LAST-MODIFIED Ignore LOCATION Required ORGANIZER Ignore PRIORITY Ignore RELATED-TO Ignore RDATE Ignore RRULE Ignore. The first instance occurs on the DTStart property. If implemented, VTIMEZONE MUST also be implemented. RECURRENCE-ID Required if RRULE is implemented; otherwise Ignore REQUEST-STATUS Required RESOURCES Ignore SEQUENCE Required STATUS Ignore SUMMARY Ignore TRANSP Required if FREEBUSY is implemented; otherwise Ignore URL Ignore UID Required X- Ignore
### 5.1.2 Free/Busy-Related Fallbacks 🫧
Free/busy methods get their own table, and this one has a fun rule. If you don't do the METHOD type, you *may* ignore it, but you **must** still send back the `REQUEST-STATUS` `"3.14;Unsupported capability"` 🙈
Method Fallback
PUBLISH Implementations MAY ignore the METHOD type. The REQUEST-STATUS "3.14;Unsupported capability" MUST be returned. REQUEST Implementations MAY ignore the METHOD type. The REQUEST-STATUS "3.14;Unsupported capability" MUST be returned. REPLY Implementations MAY ignore the METHOD type. The REQUEST-STATUS "3.14;Unsupported capability" MUST be returned.
iCalendar Property Fallback
CALSCALE Ignore; assume GREGORIAN. PRODID Ignore METHOD Required as described in the Method list above. VERSION Ignore
Component Property Fallback
COMMENT Ignore CONTACT Ignore DTEND Required DTSTAMP Required DTSTART Required DURATION Required FREEBUSY Required ORGANIZER Ignore REQUEST-STATUS Ignore UID Required URL Ignore X- Ignore
### 5.1.3 To-Do-Related Fallbacks ✅
Now the to-do crew 🎀
Method Fallback
PUBLISH Required REQUEST PUBLISH REPLY Required ADD Required CANCEL Required REFRESH Required COUNTER Reply with Not Supported DECLINECOUNTER Required if VTODO - COUNTER is implemented; otherwise reply with Not Supported
iCalendar Property Fallback
CALSCALE Ignore; assume GREGORIAN. PRODID Ignore METHOD Required as described in the Method list above. VERSION Ignore
To-Do-Related Components Fallback
VALARM Reply with Not Supported VTIMEZONE Required if any DateTime value refers to a time zone.
Component Property Fallback
ATTACH Ignore ATTENDEE Required if REQUEST is not implemented; otherwise ignore CATEGORIES Ignore CLASS Ignore COMMENT Ignore COMPLETED Required CONTACT Ignore CREATED Ignore DESCRIPTION Required DUE Required DURATION Ignore Reply with Not Supported DTSTAMP Required DTSTART Required EXDATE Ignore Reply with Not Supported EXRULE Ignore Reply with Not Supported. If implemented, VTIMEZONE MUST also be implemented. LAST-MODIFIED Ignore LOCATION Ignore ORGANIZER Ignore PERCENT-COMPLETE Ignore PRIORITY Required RECURRENCE-ID Ignore RELATED-TO Ignore REQUEST-STATUS Ignore RDATE Ignore RRULE Ignore. The first instance occurs on the DTSTART property. If implemented, VTIMEZONE MUST also be implemented. RESOURCES Ignore SEQUENCE Required STATUS Required SUMMARY Ignore URL Ignore UID Required X- Ignore
### 5.1.4 Journal-Related Fallbacks 📓
Last but not least, the journal methods and properties 💜
Method Fallback
PUBLISH Implementations MAY ignore the METHOD type. The REQUEST-STATUS "3.14;Unsupported capability" MUST be returned. ADD Implementations MAY ignore the METHOD type. The REQUEST-STATUS "3.14;Unsupported capability" MUST be returned. CANCEL Implementations MAY ignore the METHOD type. The REQUEST-STATUS "3.14;Unsupported capability" MUST be returned.
iCalendar Property Fallback
CALSCALE Ignore; assume GREGORIAN. PRODID Ignore METHOD Required as described in the Method list above. VERSION Ignore
Journal-Related Components Fallback
VTIMEZONE Required if any DateTime value refers to a time zone.
Component Property Fallback
ATTACH Ignore ATTENDEE Required if JOURNAL-REQUEST is implemented; otherwise ignore CATEGORIES Ignore CLASS Ignore COMMENT Ignore CONTACT Ignore CREATED Ignore DESCRIPTION Required DTSTAMP Required DTSTART Required EXDATE Ignore EXRULE Ignore Reply with Not Supported. If implemented, VTIMEZONE MUST also be implemented. LAST-MODIFIED Ignore ORGANIZER Ignore RECURRENCE-ID Ignore RELATED-TO Ignore RDATE Ignore. RRULE Ignore. The first instance occurs on the DTSTART property. If implemented, VTIMEZONE MUST also be implemented. SEQUENCE Required STATUS Ignore SUMMARY Required URL Ignore UID Required X- Ignore
---
## 5.2 Latency Issues ⏳
Okay so with a store-and-forward transport, events can totally arrive out of order 😭 Like, a `CANCEL` method can show up *before* the `REQUEST` it's cancelling. Here are a few of those plot twists 🍿
### 5.2.1 Cancellation of an Unknown Calendar Component.
When a `CANCEL` shows up before the original `REQUEST`, the calendar can't match the `UID` property of the cancellation to any calendar component it already has 💀 It's suggested that messages that can not be correlated, but also contain non-zero sequence numbers, get held instead of discarded 🫶 Implementations MAY age them out if no other messages arrive with the same `UID` property value and a lower sequence number ⏰
### 5.2.2 Unexpected Reply from an Unknown Delegate
This one is giving drama 🎭 When an `Attendee` delegates an item to another CU, they MUST send a `REPLY` method to the `Organizer` using the `ATTENDEE` properties, so everyone knows the request was delegated and to whom 📬 Which means an `Organizer` can get a `REPLY` from a CU that wasn't listed as one of the original `Attendees` 👀 How that gets resolved is up to the implementation, but the calendaring software is expected to either accept the reply or hold it until the related `REPLY` method comes in from the `Delegator` 🧠 And if the version of the `REPLY` method is out of date, the `Organizer` SHOULD treat the message as a `REFRESH` message and update the delegate with the correct version 🔄
### 5.3 Sequence Number
Under some conditions, a CUA may receive requests and replies with the same `SEQUENCE` property value 😵💫 That's when the `DTSTAMP` property steps in as the tie-breaker whenever two items with the same `SEQUENCE` property value get evaluated 🎀
---
# 6 Security Considerations 🔐
ITIP is an abstract transport protocol that will be bound to a real-time transport, a store-and-forward transport, and maybe other transports 🚚 The transport protocol is responsible for providing facilities for authentication and encryption, using standard Internet mechanisms that are mutually understood between the sender and receiver 🛡️
## 6.1 Security Threats 😱
### 6.1.1 Spoofing the "Organizer"
> This one is seriously important, so read it twice 🚨
In iTIP, the `Organizer` (or someone working on the `Organizer`'s behalf) is the only person authorized to make changes to an existing `VEVENT`, `VTODO`, `VJOURNAL` calendar component and republish it or redistribute updates to the `Attendees`. An iCalendar object that maliciously changes or cancels an existing `VEVENT`, `VTODO` or `VJOURNAL` calendar component can be constructed by someone other than the `Organizer` and then republished or sent to the `Attendees` 💀
### 6.1.2 Spoofing the "Attendee"
In iTIP, an `Attendee` of a `VEVENT` or `VTODO` calendar component (or someone working on the `Attendee`'s behalf) is the only person authorized to update any parameter associated with their `ATTENDEE` property and send it to the `Organizer`. An iCalendar object that maliciously changes the `ATTENDEE` parameters can be constructed by someone other than the real `Attendee` and sent to the `Organizer` 🙅♀️
### 6.1.3 Unauthorized Replacement of the Organizer
Sometimes `Attendees` of an event or to-do decide, using out-of-band mechanisms, that the `Organizer` has to be replaced 🔁 When the new `Organizer` sends out the updated `VEVENT` or `VTODO`, the `Attendee`'s CUA will detect that the `Organizer` has changed, but it has no way of knowing whether or not the change was mutually agreed upon 🤷♀️
### 6.1.4 Eavesdropping
The iCalendar object is built with human-readable clear text 👀 So any information contained in an iCalendar object may be read and/or changed by unauthorized persons while the object is in transit 🚨
### 6.1.5 Flooding a Calendar 🌊
Okay so implementations MAY provide a way to automatically drop "REQUEST" methods straight into a calendar 📅. The tea? That opens the door for a calendar to get absolutely flooded with requests, which basically blocks off all of the calendar's free time 😭🫠. Not the vibe!
### 6.1.6 Procedural Alarms 🚨
The "REQUEST" methods for "VEVENT" and "VTODO" calendar components MAY contain "VALARM" calendar components 🔔. The "VALARM" component may be of type "PROCEDURE" and MAY have an attachment containing an executable program 👀. So if an implementation takes these kinds of alarms, it's on the hook for any virus or malicious attack that might happen when that attachment gets run 💀. Bestie, be careful with this one!
### 6.1.7 Unauthorized REFRESH Requests 🙅♀️
It's possible for an "Organizer" to get a "REFRESH" request from someone who is not an "Attendee" of an event or to-do 📨. Only "Attendee's" of an event or to-do are authorized to receive replies to "REFRESH" requests. Replying to these requests for anyone who isn't an "Attendee" may be a security problem 🚩.
## 6.2 Recommendations 🎀
Okay, this part is super important ✨. For an application where the info is sensitive or critical, and the network is subject to a high probability of attack, iTIP transactions SHOULD be encrypted 🔐. This can be done with public key technology, specifically Security Multiparts for MIME [RFC-1847] in the iTIP transport binding. It helps mitigate spoofing, eavesdropping and malicious changes in transit, which is literally the whole point 💖.
### 6.2.1 Use of [RFC-1847] to secure iTIP transactions 🔏
iTIP transport bindings MUST provide a mechanism based on Security Multiparts for MIME [RFC-1847] to enable authentication of the sender's identity, and privacy and integrity of the data being transmitted 🫶. This lets the receiver of a signed iCalendar object verify who the sender is. That sender can then be correlated to an "ATTENDEE" property in the iCalendar object. If the correlation is made and the sender is authorized to make the requested change or update, then the operation may proceed ✅. It also lets the message be encrypted, so nobody unauthorized can read the contents in transit 🕵️♀️. The iTIP transport binding documents explain this process in detail 📖.
Implementations MAY provide controls for users to disable this capability 🙈.
### 6.2.2 Implementation Controls 🛠️
The threat of unauthorized replacement of the "Organizer" SHOULD be mitigated by a calendar system that uses this protocol. It can do that by providing controls or alerts that make "Calendar Users" aware of "Organizer" changes, and by letting them decide whether or not the request should be honored 👑.
The threat of flooding a calendar SHOULD be mitigated by a calendar system that uses this protocol. It can do that by providing controls that may be used to limit the acceptable sources for iTIP transactions, and perhaps the size of messages and volume of traffic, by source 🚧.
The threat of malicious procedural alarms SHOULD be mitigated by a calendar system that uses this protocol. It can do that by providing controls that may be used to disallow procedural alarms in iTIP transactions, and/or remove all alarms from the object before delivery to the recipient 🧹.
The threat of unauthorized "REFRESH" requests SHOULD be mitigated by a calendar system that uses this protocol. It can do that by providing controls or alerts that allow a "Calendar User" to decide whether or not the request should be honored 🤔. An implementation MAY decide to keep track of "Calendar Users" who were part of an attendee list and were later uninvited, for audit or historical purposes 📚. Similar controls or alerts should be provided when a "REFRESH" request is received from these "Calendar Users" too 🌸.
---
# 7 Acknowledgments 🙌
A hearty thanks to the following individuals, who helped with drafting, reviewing and discussing this memo, you're all iconic 👑: Anik Ganguly, Dan Hickman, Paul Hill, Daryl Huff, Bruce Kahn, Antoine Leca, Bob Mahoney, John Noerenberg, Leo Parker, John Rose, Doug Royer, Vinod Seraphin, Richard Shusterman, Derik Stenerson, John Sun, Alexander Taler, Kevin Tsurutome 💖.
# 8 Bibliography 📚
[iCAL] Dawson, F. and D. Stenerson, "Internet Calendaring and Scheduling Core Object Specification - iCalendar", RFC 2445, November 1998.
[iMIP] Dawson, F., Mansour, S. and S. Silverberg, "iCalendar Message-Based Interoperability Protocol - iMIP", RFC 2447, November 1998.
[RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[US-ASCII] Coded Character Set--7-bit American Standard Code for Information Interchange, ANSI X3.4-1986.
# 9 Authors' Addresses 💌
<lavender>The following address information is provided in a vCard v3.0, Electronic Business Card, format. 💅</lavender>
The authors of this memo are:
BEGIN:VCARD VERSION:3.0 N:Dawson;Frank FN:Frank Dawson ORG:Lotus Development Corporation ADR;WORK;POSTAL;PARCEL:;;6544 Battleford Drive;Raleigh;NC;27613- 3502;USA TEL;TYPE=WORK,MSG:+1-919-676-9515 TEL;TYPE=WORK,FAX:+1-919-676-9564 EMAIL;TYPE=PREF,INTERNET:Frank_Dawson@Lotus.com EMAIL;TYPE=INTERNET:fdawson@earthlink.net URL:http://home.earthlink.net/~fdawson END:VCARD
BEGIN:VCARD VERSION:3.0 N:Hopson;Ross FN:Ross Hopson ORG:On Technology, Inc. ADR;TYPE=WORK,POSTAL,PARCEL:;Suite 1600;434 Fayetteville St. Mall, Two Hannover Square;Raleigh;NC;27601 TEL;TYPE=WORK,MSG:+1-919-890-4036 TEL;TYPE=WORK,FAX:+1-919-890-4100 EMAIL;TYPE=INTERNET:rhopson@on.com END:VCARD
BEGIN:VCARD VERSION:3.0 N:Mansour;Steve FN:Steve Mansour ORG:Netscape Communications Corporation ADR;TYPE=WORK,POSTAL,PARCEL:;;501 East Middlefield Road;Mountain View;CA;94043;USA TEL;TYPE=WORK,MSG:+1-650-937-2378 TEL;TYPE=WORK,FAX:+1-650-937-2103 EMAIL;TYPE=INTERNET:sman@netscape.com END:VCARD
BEGIN:VCARD VERSION:3.0 N:Silverberg;Steve FN:Steve Silverberg ORG:Microsoft Corporation ADR;TYPE=WORK,POSTAL,PARCEL:;;One Microsoft Way; Redmond;WA;98052-6399;USA TEL;TYPE=WORK,MSG:+1-425-936-9277 TEL;TYPE=WORK,FAX:+1-425-936-8019 EMAIL;INTERNET:stevesil@Microsoft.com END:VCARD
The iCalendar object is a result of the work of the Internet Engineering Task Force Calendaring and scheduling Working Group. The chairman of that working group is: 🧚
BEGIN:VCARD VERSION:3.0 N:Ganguly;Anik FN:Anik Ganguly ORG:Open Text Inc. ADR;TYPE=WORK,POSTAL,PARCEL:;Suite 101;38777 West Six Mile Road; Livonia;MI;48152;USA TEL;TYPE=WORK,MSG:+1-734-542-5955 EMAIL;TYPE=INTERNET:ganguly@acm.org END:VCARD
The co-chairman of that working group is: 🌈
BEGIN:VCARD VERSION:3.0 N:Moskowitz;Robert FN:Robert Moskowitz NICKNAME:Bob EMAIL; TYPE=INTERNET:rgm-ietf@htt-consult.com END:VCARD
# 10. Full Copyright Statement ⭐
Here's the legal stuff, and yes it has to be kept complete 🫡.
Copyright (C) The Internet Society (1998). All Rights Reserved.
This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English.
The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
📦 where this page comes from
- ietf: rfc2446 1998-11
- 💖 girlified by claude-haiku-5-5 on : a language model's rewrite of the original, under its terms