Date::Calc(3)
okay so bestie, welcome to Date::Calc(3) — straight from the User Contributed Perl Documentation corner of the universe. This page is giving Gregorian calendar date calculations, and it is lowkey a whole toolbox. 💅✨
💖 NAME 💖
Date::Calc — Gregorian calendar date calculations. That’s the name, that’s the vibe, and honestly? Iconic.
🌟 MOTTO 🌟
Keep it small, fast and simple
🦋 PREFACE 🦋
Okay so this package consists of a C library and a Perl module (which uses the C library, internally) for all kinds of date calculations based on the Gregorian calendar (the one used in all western countries today), and it complies with all the relevant norms and standards: ISO/R 2015-1971, DIN 1355 and, to some extent, ISO 8601 (where applicable). 🫶
There’s also a scan of part of the "DIN 1355" document (in German) at http://www.engelschall.com/u/sb/download/Date-Calc/DIN1355/ if you’re curious, iykyk.
The module of course handles year numbers of 2000 and above correctly ("Year 2000" or "Y2K" compliance) — actually all year numbers from 1 to the largest positive integer representable on your system (which is at least 32767) can be dealt with. Slay. ✨
This is not true, however, for the import/export functions in this package, which are an interface to the internal POSIX date and time functions of your system, and those can only cover dates in the following ranges:
01-Jan-1970 00:00:00 GMT .. 19-Jan-2038 03:14:07 GMT [Unix etc.]
01-Jan-1904 00:00:00 LT .. 06-Feb-2040 06:28:15 LT [MacOS Classic]
(LT = local time)Note that this package projects the Gregorian calendar back until the year 1 A.D. — even though the Gregorian calendar was only adopted in 1582, mostly by the Catholic European countries, in obedience to the corresponding decree of Pope Gregory XIII in that year. History lesson and calendar lesson at the same time, honestly. 📜
Some (mainly protestant) countries continued to use the Julian calendar (used until then) until as late as the beginning of the 20th century.
Finally, note that this package is not intended to do everything you could ever imagine automagically for you; it is rather intended to serve as a toolbox (in the best of UNIX spirit and traditions) which should, however, always get you where you want to go. That’s the whole point, bestie. 🧰💅
See the section "RECIPES" at the bottom of this document for solutions to common problems!
If nevertheless you can’t figure out how to solve a particular problem, please let me know! (See e-mail address at the end of this document.) 🫶
🦋 SYNOPSIS 🦋
Here’s the whole synopsis, literally every import and every signature, untouched because we do not mess with code in this group chat:
use Date::Calc qw(
Days_in_Year
Days_in_Month
Weeks_in_Year
leap_year
check_date
check_time
check_business_date
Day_of_Year
Date_to_Days
Day_of_Week
Week_Number
Week_of_Year
Monday_of_Week
Nth_Weekday_of_Month_Year
Standard_to_Business
Business_to_Standard
Delta_Days
Delta_DHMS
Delta_YMD
Delta_YMDHMS
N_Delta_YMD
N_Delta_YMDHMS
Normalize_DHMS
Add_Delta_Days
Add_Delta_DHMS
Add_Delta_YM
Add_Delta_YMD
Add_Delta_YMDHMS
Add_N_Delta_YMD
Add_N_Delta_YMDHMS
System_Clock
Today
Now
Today_and_Now
This_Year
Gmtime
Localtime
Mktime
Timezone
Date_to_Time
Time_to_Date
Easter_Sunday
Decode_Month
Decode_Day_of_Week
Decode_Language
Decode_Date_EU
Decode_Date_US
Fixed_Window
Moving_Window
Compress
Uncompress
check_compressed
Compressed_to_Text
Date_to_Text
Date_to_Text_Long
English_Ordinal
Calendar
Month_to_Text
Day_of_Week_to_Text
Day_of_Week_Abbreviation
Language_to_Text
Language
Languages
Decode_Date_EU2
Decode_Date_US2
Parse_Date
ISO_LC
ISO_UC
);
use Date::Calc qw(:all);
Days_in_Year
$days = Days_in_Year($year,$month);
Days_in_Month
$days = Days_in_Month($year,$month);
Weeks_in_Year
$weeks = Weeks_in_Year($year);
leap_year
if (leap_year($year))
check_date
if (check_date($year,$month,$day))
check_time
if (check_time($hour,$min,$sec))
check_business_date
if (check_business_date($year,$week,$dow))
Day_of_Year
$doy = Day_of_Year($year,$month,$day);
Date_to_Days
$days = Date_to_Days($year,$month,$day);
Day_of_Week
$dow = Day_of_Week($year,$month,$day);
Week_Number
$week = Week_Number($year,$month,$day); # DEPRECATED
Week_of_Year
($week,$year) = Week_of_Year($year,$month,$day); # RECOMMENDED
$week = Week_of_Year($year,$month,$day); # DANGEROUS
Monday_of_Week
($year,$month,$day) = Monday_of_Week($week,$year);
Nth_Weekday_of_Month_Year
if (($year,$month,$day) =
Nth_Weekday_of_Month_Year($year,$month,$dow,$n))
Standard_to_Business
($year,$week,$dow) =
Standard_to_Business($year,$month,$day);
Business_to_Standard
($year,$month,$day) =
Business_to_Standard($year,$week,$dow);
Delta_Days
$Dd = Delta_Days($year1,$month1,$day1,
$year2,$month2,$day2);
Delta_DHMS
($Dd,$Dh,$Dm,$Ds) =
Delta_DHMS($year1,$month1,$day1, $hour1,$min1,$sec1,
$year2,$month2,$day2, $hour2,$min2,$sec2);
Delta_YMD
($Dy,$Dm,$Dd) =
Delta_YMD($year1,$month1,$day1,
$year2,$month2,$day2);
Delta_YMDHMS
($D_y,$D_m,$D_d, $Dh,$Dm,$Ds) =
Delta_YMDHMS($year1,$month1,$day1, $hour1,$min1,$sec1,
$year2,$month2,$day2, $hour2,$min2,$sec2);
N_Delta_YMD
($Dy,$Dm,$Dd) =
N_Delta_YMD($year1,$month1,$day1,
$year2,$month2,$day2);
N_Delta_YMDHMS
($D_y,$D_m,$D_d, $Dhh,$Dmm,$Dss) =
N_Delta_YMDHMS($year1,$month1,$day1, $hour1,$min1,$sec1,
$year2,$month2,$day2, $hour2,$min2,$sec2);
Normalize_DHMS
($Dd,$Dh,$Dm,$Ds) =
Normalize_DHMS($Dd,$Dh,$Dm,$Ds);
Add_Delta_Days
($year,$month,$day) =
Add_Delta_Days($year,$month,$day,
$Dd);
Add_Delta_DHMS
($year,$month,$day, $hour,$min,$sec) =
Add_Delta_DHMS($year,$month,$day, $hour,$min,$sec,
$Dd,$Dh,$Dm,$Ds);
Add_Delta_YM
($year,$month,$day) =
Add_Delta_YM($year,$month,$day,
$Dy,$Dm);
Add_Delta_YMD
($year,$month,$day) =
Add_Delta_YMD($year,$month,$day,
$Dy,$Dm,$Dd);
Add_Delta_YMDHMS
($year,$month,$day, $hour,$min,$sec) =
Add_Delta_YMDHMS($year,$month,$day, $hour,$min,$sec,
$D_y,$D_m,$D_d, $Dh,$Dm,$Ds);
Add_N_Delta_YMD
($year,$month,$day) =
Add_N_Delta_YMD($year,$month,$day,
$Dy,$Dm,$Dd);
Add_N_Delta_YMDHMS
($year,$month,$day, $hour,$min,$sec) =
Add_N_Delta_YMDHMS($year,$month,$day, $hour,$min,$sec,
$D_y,$D_m,$D_d, $Dhh,$Dmm,$Dss);
System_Clock
($year,$month,$day, $hour,$min,$sec, $doy,$dow,$dst) =
System_Clock([$gmt]);
Today
($year,$month,$day) = Today([$gmt]);
Now
($hour,$min,$sec) = Now([$gmt]);
Today_and_Now
($year,$month,$day, $hour,$min,$sec) = Today_and_Now([$gmt]);
This_Year
$year = This_Year([$gmt]);
Gmtime
($year,$month,$day, $hour,$min,$sec, $doy,$dow,$dst) =
Gmtime([time]);
Localtime
($year,$month,$day, $hour,$min,$sec, $doy,$dow,$dst) =
Localtime([time]);
Mktime
$time = Mktime($year,$month,$day, $hour,$min,$sec);
Timezone
($D_y,$D_m,$D_d, $Dh,$Dm,$Ds, $dst) = Timezone([time]);
Date_to_Time
$time = Date_to_Time($year,$month,$day, $hour,$min,$sec);
Time_to_Date
($year,$month,$day, $hour,$min,$sec) = Time_to_Date([time]);
Easter_Sunday
($year,$month,$day) = Easter_Sunday($year);
Decode_Month
if ($month = Decode_Month($string[,$lang]))
Decode_Day_of_Week
if ($dow = Decode_Day_of_Week($string[,$lang]))
Decode_Language
if ($lang = Decode_Language($string))
Decode_Date_EU
if (($year,$month,$day) = Decode_Date_EU($string[,$lang]))
Decode_Date_US
if (($year,$month,$day) = Decode_Date_US($string[,$lang]))
Fixed_Window
$year = Fixed_Window($yy);
Moving_Window
$year = Moving_Window($yy);
Compress
$date = Compress($year,$month,$day);
Uncompress
if (($century,$year,$month,$day) = Uncompress($date))
check_compressed
if (check_compressed($date))
Compressed_to_Text
$string = Compressed_to_Text($date[,$lang]);
Date_to_Text
$string = Date_to_Text($year,$month,$day[,$lang]);
Date_to_Text_Long
$string = Date_to_Text_Long($year,$month,$day[,$lang]);
English_Ordinal
$string = English_Ordinal($number);
Calendar
$string = Calendar($year,$month[,$orthodox[,$lang]]);
Month_to_Text
$string = Month_to_Text($month[,$lang]);
Day_of_Week_to_Text
$string = Day_of_Week_to_Text($dow[,$lang]);
Day_of_Week_Abbreviation
$string = Day_of_Week_Abbreviation($dow[,$lang]);
Language_to_Text
$string = Language_to_Text($lang);
Language
$lang = Language();
Language($lang); # DEPRECATED
$oldlang = Language($newlang); # DEPRECATED
Languages
$max_lang = Languages();
Decode_Date_EU2
if (($year,$month,$day) = Decode_Date_EU2($string[,$lang]))
Decode_Date_US2
if (($year,$month,$day) = Decode_Date_US2($string[,$lang]))
Parse_Date
if (($year,$month,$day) = Parse_Date($string[,$lang]))
ISO_LC
$lower = ISO_LC($string);
ISO_UC
$upper = ISO_UC($string);
Version
$string = Date::Calc::Version();🚨 IMPORTANT NOTES 🚨
(okay bestie, real talk — peep the section "RECIPES" at the bottom of this doc for solutions to common problems! 🍓)
"Year 2000"("Y2K") compliance 👑
so the upper limit for any year number in this module is only given by the size of the largest positive integer that can be represented in a variable of the C type "int" on your system, which is at least 32767, according to the ANSI C standard (exceptions see below, bestie).
In order to simplify calculations, this module projects the gregorian calendar back until the year 1 A.D. — like, back BEYOND the year 1582 when this calendar was first decreed by the Catholic Pope Gregory XIII! 🫶
Therefore, BE SURE TO ALWAYS SPECIFY "1998" WHEN YOU MEAN "1998", for instance, and DO NOT WRITE "98" INSTEAD, because this will in fact perform a calculation based on the year "98" A.D. and NOT "1998"! 💀
An exception from this rule are the functions which contain the word "compress" in their names (which can only handle years between 1970 and 2069 and also accept the abbreviations "00" to "99"), and the functions whose names begin with "Decode_Date_" (which translate year numbers below 100 using a technique known as "moving window").
If you want to convert a two-digit year number into a full-fledged, four-digit (at least for some years to come ";-)") year number, use the two functions Fixed_Window() and Moving_Window() (see their description further below).
Note also that the following import/export functions (which are interfaces to the POSIX functions "time()", "gmtime()", "localtime()" and "mktime()" or (the last two) substitutes for the BSD function "timegm()" and the POSIX function "gmtime()") have a very limited range of representable dates (in contrast to all other functions in this package, which cover virtually any date including and after January 1st 1 A.D.):
System_Clock()
Today()
Now()
Today_and_Now()
This_Year()
Gmtime()
Localtime()
Mktime()
Timezone()
Date_to_Time()
Time_to_Date()These functions can only deal with dates in the range from 01-Jan-1970 00:00:00 GMT to 19-Jan-2038 03:14:07 GMT (the latter limit is only authoritative on 32 bit systems, however, and can (in principle, through a few code changes) be extended somewhat ":-)" on 64 bit systems).
On MacOS Classic, the valid range of dates is between (both included) 01-Jan-1904 00:00:00 (local time) to 06-Feb-2040 06:28:15 (local time).
Note further that the function Easter_Sunday() can only be used for years in the range 1583 to 2299. 🌸
- POSIX functions 🐚
Note that the following functions
Gmtime()
Localtime()
Mktime()
Timezone()are actually wrappers around or based upon the corresponding POSIX functions "time()", "gmtime()", "localtime()" and "mktime()".
As such, they depend on local settings of the underlying machine such as e.g. the system clock, the time zone and the locale.
Their results can therefore sometimes be unexpected or counter-intuitive.
Therefore, no support can be provided for these functions.
They are supplied "as is", purely for the sake of interoperability.
Use at your own risk. (You have been warned!) 😭
- First index 1️⃣
ALL ranges in this module start with "1", NOT "0"!
I.e., the day of month, day of week, day of year, month of year, week of year, first valid year number and language ALL start counting at one, NOT zero!
The only exception is the function Week_Number(), which may in fact return "0" when the given date actually lies in the last week of the PREVIOUS year, and of course the numbers for hours (0..23), minutes (0..59) and seconds (0..59).
- Function naming conventions 💅
Function names completely in lower case indicate a boolean return value. iykyk.
- Boolean values ✅
Boolean values returned from functions in this module are always a numeric zero ("0") for "false" and a numeric one ("1") for "true".
- Exception handling 🚨
The functions in this module will usually die with a corresponding error message if their input parameters, intermediate results or output values are out of range.
The following functions handle errors differently:
check_date()check_time()check_business_date()check_compressed()
(which return a "false" return value when the given input does not represent a valid date or time),
Nth_Weekday_of_Month_Year()
(which returns an empty list if the requested 5th day of week does not exist),
Decode_Month()Decode_Day_of_Week()Decode_Language()Fixed_Window()Moving_Window()Compress()
(which return "0" upon failure or invalid input), and
Decode_Date_EU()Decode_Date_US()Decode_Date_EU2()Decode_Date_US2()Parse_Date()Uncompress()
(which return an empty list upon failure or invalid input).
Note that you can always catch an exception thrown by any of the functions in this module and handle it yourself by enclosing the function call in an "eval" with curly brackets and checking the special variable "$@" (see "eval" in perlfunc(1) for details). 🫶
💖 DESCRIPTION 💖
use Date::Calc qw( Days_in_Year Days_in_Month ... );use Date::Calc qw(:all);
You can either specify the functions you want to import explicitly by enumerating them between the parentheses of the "qw()" operator, or you can use the ":all" tag instead to import ALL available functions. literally all of them, no gatekeeping 💅
$days = Days_in_Year($year,$month);
This function returns the sum of the number of days in the months starting with January up to and including $month in the given year $year.
I.e., "Days_in_Year(1998,1)" returns "31", "Days_in_Year(1998,2)" returns "59", "Days_in_Year(1998,3)" returns "90", and so on.
Note that "Days_in_Year($year,12)" returns the number of days in the given year $year, i.e., either "365" or "366". slay 🌈
$days = Days_in_Month($year,$month);
This function returns the number of days in the given month $month of the given year $year.
The year must always be supplied, even though it is only needed when the month is February, in order to determine whether it is a leap year or not. yeah she's a little extra but she's valid 🎀
I.e., "Days_in_Month(1998,1)" returns "31", "Days_in_Month(1998,2)" returns "28", "Days_in_Month(2000,2)" returns "29", "Days_in_Month(1998,3)" returns "31", and so on.
$weeks = Weeks_in_Year($year);
This function returns the number of weeks in the given year $year, i.e., either "52" or "53".
if (leap_year($year))
This function returns "true" ("1") if the given year $year is a leap year and "false" ("0") otherwise. 🐸
if (check_date($year,$month,$day))
This function returns "true" ("1") if the given three numerical values $year, $month and $day constitute a valid date, and "false" ("0") otherwise.
if (check_time($hour,$min,$sec))
This function returns "true" ("1") if the given three numerical values $hour, $min and $sec constitute a valid time (0 <= $hour < 24, 0 <= $min < 60 and 0 <= $sec < 60), and "false" ("0") otherwise. ⏰
if (check_business_date($year,$week,$dow))
This function returns "true" ("1") if the given three numerical values $year, $week and $dow constitute a valid date in business format, and "false" ("0") otherwise.
Beware that this function does NOT compute whether a given date is a business day (i.e., Monday to Friday)! 🚩
To do so, use "(Day_of_Week($year,$month,$day) < 6)" instead. fr fr
$doy = Day_of_Year($year,$month,$day);
This function returns the (relative) number of the day of the given date in the given year.
E.g., "Day_of_Year($year,1,1)" returns "1", "Day_of_Year($year,2,1)" returns "32", and "Day_of_Year($year,12,31)" returns either "365" or "366".
The day of year is sometimes also referred to as the Julian day (or date), although it has nothing to do with the Julian calendar, the calendar which was used before the Gregorian calendar. (the lore is deep, bestie 🧚)
In order to convert the number returned by this function back into a date, use the function Add_Delta_Days() (described further below), as follows:
$doy = Day_of_Year($year,$month,$day);
($year,$month,$day) = Add_Delta_Days($year,1,1, $doy - 1);$days = Date_to_Days($year,$month,$day);
This function returns the (absolute) number of the day of the given date, where counting starts at the 1st of January of the year 1 A.D.
I.e., "Date_to_Days(1,1,1)" returns "1", "Date_to_Days(1,12,31)" returns "365", "Date_to_Days(2,1,1)" returns "366", "Date_to_Days(1998,5,1)" returns "729510", and so on.
This is sometimes also referred to (not quite correctly) as the Julian date (or day). This may cause confusion, because also the number of the day in a year (from 1 to 365 or 366) is frequently called the "Julian day". 💀
More confusing still, this has nothing to do with the Julian calendar, which was used BEFORE the Gregorian calendar.
The Julian calendar was named after famous Julius Caesar, who had instituted it in Roman times. The Julian calendar is less precise than the Gregorian calendar because it has too many leap years compared to the true mean length of a year (but the Gregorian calendar also still has one day too much every 5000 years). Anyway, the Julian calendar was better than what existed before, because rulers had often changed the calendar used until then in arbitrary ways, in order to lengthen their own reign, for instance. (the audacity honestly 😭)
In order to convert the number returned by this function back into a date, use the function Add_Delta_Days() (described further below), as follows:
$days = Date_to_Days($year,$month,$day);
($year,$month,$day) = Add_Delta_Days(1,1,1, $days - 1);$dow = Day_of_Week($year,$month,$day);
This function returns the number of the day of week of the given date.
The function returns "1" for Monday, "2" for Tuesday and so on until "7" for Sunday. 🗓️
Note that in the Hebrew calendar (on which the Christian calendar is based), the week starts with Sunday and ends with the Sabbath or Saturday (where according to the Genesis (as described in the Bible) the Lord rested from creating the world).
Okay so back in medieval times, Catholic Popes have decreed the Sunday to be the official day of rest — like, the whole point was to dissociate the Christian from the Hebrew belief. 💅
It appears that this actually happened with Emperor Constantin, who converted to Christianity but still worshipped the Sun god and therefore moved the Christian sabbath to the day of the Sun. ☀️
Nowadays, the Sunday AND the Saturday are commonly considered (and used as) days of rest, usually referred to as the "week-end". 🎀
Consistent with this practice, current norms and standards (such as ISO/R 2015-1971, DIN 1355 and ISO 8601) define the Monday as the first day of the week. ✨
$week = Week_Number($year,$month,$day);— this function returns the number of the week the given date lies in. If the given date lies in the LAST week of the PREVIOUS year,0is returned. If the given date lies in the FIRST week of the NEXT year,Weeks_in_Year($year) + 1is returned. 🗓️($week,$year) = Week_of_Year($year,$month,$day);— this function returns the number of the week the given date lies in, as well as the year that week belongs to. I.e., if the given date lies in the LAST week of the PREVIOUS year,(Weeks_in_Year($year-1), $year-1)is returned. If the given date lies in the FIRST week of the NEXT year,(1, $year+1)is returned. Otherwise,(Week_Number($year,$month,$day), $year)is returned. 💖$week = Week_of_Year($year,$month,$day);— in scalar context, this function returns just the week number. This allows you to write$week = Week_of_Year($year,$month,$day);instead of($week) = Week_of_Year($year,$month,$day);(note the parentheses around$week). If the given date lies in the LAST week of the PREVIOUS year,Weeks_in_Year($year-1)is returned. If the given date lies in the FIRST week of the NEXT year,1is returned. Otherwise the return value is identical with that ofWeek_Number($year,$month,$day).
BEWARE that using this function in scalar context is a DANGEROUS feature, because without knowing which year the week belongs to, you might inadvertently assume the wrong one! 😭 If for instance you are iterating through an interval of dates, you might assume that the week always belongs to the same year as the given date, which unfortunately is WRONG in some cases! In many years, the 31st of December for instance belongs to week number one of the FOLLOWING year. Assuming that the year is the same as your date (31st of December, in this example), sends you back to the first week of the CURRENT year — the Monday of which, by the way, in case of bad luck, might actually lie in the year BEFORE the current year! This actually happens in 2002, for example. So you always need to provide the correct corresponding year number by other means, keeping track of it yourself. In case you do not understand this, never mind, but then simply DO NOT USE this function in scalar context! 💀
($year,$month,$day) = Monday_of_Week($week,$year);— this function returns the date of the first day of the given week, i.e., the Monday.$yearmust be greater than or equal to1, and$weekmust lie in the range1toWeeks_in_Year($year). 🫶
Note that you can write ($year,$month,$day) = Monday_of_Week(Week_of_Year($year,$month,$day)); in order to calculate the date of the Monday of the same week as the given date. If you want to calculate any other day of week in the same week as a given date, use
@date = Add_Delta_Days(Monday_of_Week(Week_of_Year(@date)),$offset);where $offset = 1 for Tuesday, 2 for Wednesday etc. 🌸
if (($year,$month,$day) = Nth_Weekday_of_Month_Year($year,$month,$dow,$n))— this function calculates the date of the$nth day of week$dowin the given month$monthand year$year; such as, for example, the 3rd Thursday of a given month and year. This can be used to send a notification mail to the members of a group which meets regularly on every 3rd Thursday of a month, for instance. (See the sectionRECIPESnear the end of this document for a code snippet to actually do so.) 📬
$year must be greater than or equal to 1, $month must lie in the range 1 to 12, $dow must lie in the range 1 to 7 and $n must lie in the range 1 to 5, or a fatal error (with appropriate error message) occurs. The function returns an empty list when the 5th of a given day of week does not exist in the given month and year. 😭
($year,$week,$dow) = Standard_to_Business($year,$month,$day);— this function converts a given date from standard notation (year, month, day (of month)) to business notation (year, week, day of week). 🔁($year,$month,$day) = Business_to_Standard($year,$week,$dow);— this function converts a given date from business notation (year, week, day of week) to standard notation (year, month, day (of month)). 🎀$Dd = Delta_Days($year1,$month1,$day1, $year2,$month2,$day2);— this function returns the difference in days between the two given dates. The result is positive if the two dates are in chronological order, i.e., if date #1 comes chronologically BEFORE date #2, and negative if the order of the two dates is reversed. The result is zero if the two dates are identical. 🦋($Dd,$Dh,$Dm,$Ds) = Delta_DHMS($year1,$month1,$day1, $hour1,$min1,$sec1, $year2,$month2,$day2, $hour2,$min2,$sec2);— this function returns the difference in days, hours, minutes and seconds between the two given dates with times. All four return values will be positive if the two dates are in chronological order, i.e., if date #1 comes chronologically BEFORE date #2, and negative (in all four return values!) if the order of the two dates is reversed. This is so that the two functionsDelta_DHMS()andAdd_Delta_DHMS()(description see further below) are complementary, i.e., mutually inverse:
Add_Delta_DHMS(@date1,@time1, Delta_DHMS(@date1,@time1, @date2,@time2))yields (@date2,@time2) again, whereas
Add_Delta_DHMS(@date2,@time2,
map(-$_, Delta_DHMS(@date1,@time1, @date2,@time2)))yields (@date1,@time1), and
Delta_DHMS(@date1,@time1, Add_Delta_DHMS(@date1,@time1, @delta))yields @delta again. The result is zero (in all four return values) if the two dates and times are identical. ⏰
($Dy,$Dm,$Dd) = Delta_YMD($year1,$month1,$day1, $year2,$month2,$day2);— this function returns the vector
( $year2 - $year1, $month2 - $month1, $day2 - $day1 )This is called the "one-by-one" semantics. Adding the result of this function to the first date always yields the second date again, and adding the negative result (where the signs of all elements of the result vector have been flipped) to the second date gives the first date. See also the description of the function Add_Delta_YMD() further below. 🧚
Example:
(6,2,-30) == Delta_YMD(1996,1,31, 2002,3,1]);
[1996,1,31] + ( 6, 2,-30) = [2002,3, 1]
[2002,3, 1] + (-6,-2, 30) = [1996,1,31]An error occurs if any of the two given dates is invalid. 💜
($D_y,$D_m,$D_d, $Dh,$Dm,$Ds) = Delta_YMDHMS($year1,$month1,$day1, $hour1,$min1,$sec1, $year2,$month2,$day2, $hour2,$min2,$sec2);— this function is based on the functionDelta_YMD()above but additionally calculates the time difference. When a carry over from the time difference occurs, the value of$D_dis adjusted accordingly, thus giving the correct total date/time difference. 🕰️
Arguments are expected to be in chronological order to yield a (usually) positive result. In any case, adding the result of this function to the first date/time value ($year1,$month1,$day1, $hour1,$min1,$sec1) always gives the second date/time value ($year2,$month2,$day2, $hour2,$min2,$sec2) again, and adding the negative result (with the signs of all elements of the result vector flipped) to the second date/time value gives the first date/time value. See the function Add_Delta_YMDHMS() further below for adding a date/time value and a date/time difference. An error occurs if any of the given two date/time values is invalid. 🔥
($Dy,$Dm,$Dd) = N_Delta_YMD($year1,$month1,$day1, $year2,$month2,$day2);— this function returns the difference between the two given dates in a more intuitive way (as far as possible - more on that see a bit further below) than the functionDelta_YMD()described above. TheNwhich precedes its name is meant to signify "new" or "normalized". 🌈
This function is loosely based on recipe #17 b) (see the section RECIPES below near the end of this document). However, the code of recipe #17 b) actually does not treat positive and negative values symmetrically and consistently. This new routine does. 👑
The return values of this function are guaranteed to all have the same sign (or to be zero). This is why this function is called "normalized". Moreover, the results are guaranteed to be "minimal", in the sense that |$Dm| < 12 and |$Dd| < 31 (which is equivalent to $Dm lying in the range [-11..+11] and $Dd lying in the range [-30..+30]). ✨
When the results are applied (i.e., added) to the first given date in a left-to-right order, the second given date is guaranteed to be obtained, provided that intermediary results are truncated, as done by the function Add_Delta_YM() (see further below), i.e., that invalid intermediate dates such as e.g. [2009,2,31] will automatically be transformed into [2009,2,28] (and not "wrapped" into the next month, e.g. to [2009,3,3]). This is called the "left-to-right with truncation" semantics. 🎀
Note that reversing the order of the given dates and reversing the sign of each of the result values will not always add up. Consider the dates [2008,2,29] and [2009,2,1]: their difference is (0,11,3) ([2008,2,29] plus 11 months is [2009,1,29], which plus 3 days is [2009,2,1]), but the difference between [2009,2,1] and [2008,2,29] is (0,-11,-1), and not (0,-11,-3) ([2009,2,1] minus 11 months is [2008,3,1], which minus one day is [2008,2,29]). 😭
Another example: The difference between [1996,2,29] and [1997,2,28] is (1,0,0) (observe the truncation of the invalid date [1997,2,29] to [1997,2,28] here!), whereas the difference between [1997,2,28] and [1996,2,29] is (0,-11,-28) ([1997,2,28] minus 11 months is [1996,3,28], which minus 28 days is not [1996,3,0] but of course [1996,2,29]). 💀
okay so the benign examples — such as for instance the difference between [1964,1,3] and [2009,9,10] — are completely symmetrical 💅: the difference in this example is (45,8,7), whereas the difference between [2009,9,10] and [1964,1,3] is (-45,-8,-7), as would normally be expected. In this example, the result is also the same as the one returned by Delta_YMD(). ✨
All these counter-intuitive effects are due to the fact that months (and due to leap years, also years) do not correspond to a fixed number of days, so the semantics of "plus one month" or "plus one year" are in fact undefined. 😭
The present function is an attempt to provide a definition which is intuitive most of the time, and at least consistent the rest of the time.
Other definitions are of course possible, but most often lead to contradictions (e.g., the results and the given first date do not add up to the second given date).
See the file datecalc.pl in the examples subdirectory of this distribution for a way to play around with this function, or go to http://www.engelschall.com/u/sb/datecalc/ for the online version. 🧚
An error occurs if any of the two given dates is invalid, or if any intermediate result leads to an invalid date (this does not apply to truncation, however, as explained above).
($D_y,$D_m,$D_d, $Dhh,$Dmm,$Dss) = N_Delta_YMDHMS($year1,$month1,$day1, $hour1,$min1,$sec1, $year2,$month2,$day2, $hour2,$min2,$sec2);— this function essentially does the same as the functionN_Delta_YMD()described immediately above, except that also the difference in hours, minutes and seconds is taken into account. This function is loosely based on recipe #17 a) (see the sectionRECIPESbelow near the end of this document). However, the code of recipe #17 a) actually does not treat positive and negative values symmetrically and consistently. This new routine does. The return values of this function (including the time differences) are guaranteed to all have the same sign (or to be zero). This is the reason for theNthat precedes the name of this function, which is intended to mean "normalized" (or "new"). Moreover, the results are guaranteed to be "minimal", in the sense that|$D_m| < 12,|$D_d| < 31,|$Dhh| < 24,|$Dmm| < 60and|$Dss| < 60(which is equivalent to$D_mlying in the range[-11..+11],$D_dlying in the range[-30..+30],$Dhhlying in the range[-23..+23], and$Dmmand$Dssboth lying in the range[-59..+59]). 🔥($Dd,$Dh,$Dm,$Ds) = Normalize_DHMS($Dd,$Dh,$Dm,$Ds);— this function takes four arbitrary values for days, hours, minutes and seconds (which may have different signs) and renormalizes them so that the values for hours, minutes and seconds will lie in the ranges[-23..23],[-59..59]and[-59..59], respectively, and so that all four values have the same sign (or are zero). The given values are left untouched, i.e., unchanged. 🫶($year,$month,$day) = Add_Delta_Days($year,$month,$day, $Dd);— this function has two principal uses. First, it can be used to calculate a new date, given an initial date and an offset (which may be positive or negative) in days, in order to answer questions like "today plus 90 days -- which date gives that?". (In order to add a weeks offset, simply multiply the weeks offset with7and use that as your days offset.) Second, it can be used to convert the canonical representation of a date, i.e., the number of that day (where counting starts at the 1st of January in 1 A.D.), back into a date given as year, month and day. Because counting starts at1, you will actually have to subtract1from the canonical date in order to get back the original date:
$canonical = Date_to_Days($year,$month,$day);
($year,$month,$day) = Add_Delta_Days(1,1,1, $canonical - 1);Moreover, this function is the inverse of the function Delta_Days():
Add_Delta_Days(@date1, Delta_Days(@date1, @date2))yields @date2 again, whereas
Add_Delta_Days(@date2, -Delta_Days(@date1, @date2))yields @date1, and
Delta_Days(@date1, Add_Delta_Days(@date1, $delta))yields $delta again. 💖
($year,$month,$day, $hour,$min,$sec) = Add_Delta_DHMS($year,$month,$day, $hour,$min,$sec, $Dd,$Dh,$Dm,$Ds);— this function serves to add a days, hours, minutes and seconds offset to a given date and time, in order to answer questions like "today and now plus 7 days but minus 5 hours and then plus 30 minutes, what date and time gives that?":
($y,$m,$d,$H,$M,$S) = Add_Delta_DHMS(Today_and_Now(), +7,-5,+30,0);($year,$month,$day) = Add_Delta_YM($year,$month,$day, $Dy,$Dm);— this function can be used to add a year and/or month offset to a given date. In contrast to the function described immediately below (Add_Delta_YMD()), this function does no "wrapping" into the next month if the day happens to lie outside the valid range for the resulting year and month (after adding the year and month offsets). Instead, it simply truncates the day to the last possible day of the resulting month. Examples: adding an offset of 0 years, 1 month to the date[1999,1,31]would result in the (invalid) date[1999,2,31]. The function replaces this result by the (valid) date[1999,2,28]. Adding an offset of 1 year, 1 month to the same date[1999,1,31]as above would result in the (still invalid) date[2000,2,31]. The function replaces this result by the valid date[2000,2,29](because 2000 is a leap year). Note that the year and month offsets can be negative, and that they can have different signs. If you want to additionally add a days offset, use the functionAdd_Delta_Days()before or after callingAdd_Delta_YM():
@date2 = Add_Delta_Days( Add_Delta_YM(@date1, $Dy,$Dm), $Dd );
@date2 = Add_Delta_YM( Add_Delta_Days(@date1, $Dd), $Dy,$Dm );Note that your result may depend on the order in which you call these two functions! Consider the date [1999,2,28] and the offsets 0 years, 1 month and 1 day: [1999,2,28] plus one month is [1999,3,28], plus one day is [1999,3,29]. [1999,2,28] plus one day is [1999,3,1], plus one month is [1999,4,1]. (Which is also the reason why the Add_Delta_YM() function does not allow to add a days offset, because this would actually require TWO functions: One for adding the days offset BEFORE and one for adding it AFTER applying the year/month offsets.)
An error occurs if the initial date is not valid.
Note that Add_Delta_YM( Add_Delta_YM(@date, $Dy,$Dm), -$Dy,-$Dm ); will not, in general, return the original date @date (consider the examples given above!). 😭
($year,$month,$day) = Add_Delta_YMD($year,$month,$day, $Dy,$Dm,$Dd);— this function serves to add a years, months and days offset to a given date. (In order to add a weeks offset, simply multiply the weeks offset with7and add this number to your days offset.) Note that the three offsets for years, months and days are applied independently from each other. This also allows them to have different signs. The years and months offsets are applied first, and the days offset is applied last. If the resulting date happens to fall on a day after the end of the resulting month, like the 32nd of April or the 30th of February, then the date is simply counted forward into the next month (possibly also into the next year) by the number of excessive days (e.g., the 32nd of April will become the 2nd of May).
BEWARE that this behaviour differs from that of previous versions of this module! In previous versions, the day was simply truncated to the maximum number of days in the resulting month. If you want the previous behaviour, use the new functionAdd_Delta_YM()(described immediately above) plus the functionAdd_Delta_Days()instead.
BEWARE also that because a year and a month offset is not equivalent to a fixed number of days, the transformation performed by this function is NOT ALWAYS REVERSIBLE! This is in contrast to the functionsAdd_Delta_Days()andAdd_Delta_DHMS(), which are fully and truly reversible (with the help of the functionsDelta_Days()andDelta_DHMS(), for instance).
Note that for this same reason,
@date = Add_Delta_YMD(
Add_Delta_YMD(@date, $Dy,$Dm,$Dd), -$Dy,-$Dm,-$Dd);will in general NOT return the initial date @date, even though
@date2 = Add_Delta_YMD( @date1, Delta_YMD(@date1, @date2) );will always return the second date @date2, and
@date1 = Add_Delta_YMD( @date2, map(-$_, Delta_YMD(@date1, @date2)) );which is the same as
@date1 = Add_Delta_YMD( @date2, Delta_YMD(@date2, @date1) );will always return the first date @date1.
Examples:
[1996,1,31] + ( 6, 1,-2) = [2002,3,1]
[2002,3, 1] + (-6,-1, 2) = [1996,2,3] # EXPECTED: [1996,1,31]
(6,2,-30) == Delta_YMD(1996,1,31, 2002,3,1);
[1996,1,31] + ( 6, 2,-30) = [2002,3, 1]
[2002,3, 1] + (-6,-2, 30) = [1996,1,31] # OK
(6,1,-2) == Delta_YMD(1996,2,3, 2002,3,1);
[1996,2,3] + ( 6, 1,-2) = [2002,3,1]
[2002,3,1] + (-6,-1, 2) = [1996,2,3] # OKNote that this is NOT a program bug but NECESSARILY so, because of the variable lengths of years and months, and hence because of the ambiguity of the difference between two dates in terms of years, months and days, i.e., the fact that the difference between two dates can be expressed in more than one way:
[1996,1,31] + (6,1, -2) = [2002,3,1]
[1996,1,31] + (6,2,-30) = [2002,3,1]($year,$month,$day, $hour,$min,$sec) = Add_Delta_YMDHMS($year,$month,$day, $hour,$min,$sec, $D_y,$D_m,$D_d, $Dh,$Dm,$Ds);— same as the function above, except that a time offset may be given in addition to the year, month and day offset. ⭐($year,$month,$day) = Add_N_Delta_YMD($year,$month,$day, $Dy,$Dm,$Dd);— this function is actually a shortcut for applying the functionAdd_Delta_YM()first, followed by the functionAdd_Delta_Days(), i.e., this function does exactly the same as
($year,$month,$day) = Add_Delta_Days( Add_Delta_YM($year,$month,$day,$Dy,$Dm), $Dd );Beware that, if necessary, the function Add_Delta_YM() truncates the resulting day of the month to the largest allowable value for that month, i.e., the (invalid) result [2009,2,31] is automatically transformed into [2009,2,28]. For more details on this truncation, see the description of the function Add_Delta_YM() further above. 🦋
Okay so bestie, this next bit is genuinely the complement tea ☕ — this function is meant to be complementary with the function N_Delta_YMD() described further above (you remember her, she's iconic).
What that means in practice: it is guaranteed that the result returned by
Add_N_Delta_YMD( @date1, N_Delta_YMD(@date1, @date2) );is always identical with the given date @date2. Slay, no cap. 🎀
But — and this is the plot twist 💀 — unlike with function Add_Delta_YMD(), the reverse is not true here, i.e.
($Dy,$Dm,$Dd) = N_Delta_YMD(@date1,@date2);
@date = Add_N_Delta_YMD(@date2, -$Dy,-$Dm,-$Dd);will NOT always return the initial date @date1. Yeah. She's not symmetric, and that's just her vibe. 🦋
Example (watch the math do its little dance):
(0,11,3) == N_Delta_YMD(2008,2,29, 2009,2,1);
[2008,2,29] + (0, 11, 3) = [2009,2, 1]
[2009,2, 1] + (0,-11,-3) = [2008,2,27] # EXPECTED: [2008,2,29]See how it lands on the 27th instead of the 29th? That's not a bug, that's just how this one behaves — leap day got left on read 😭
($year,$month,$day, $hour,$min,$sec) = Add_N_Delta_YMDHMS($year,$month,$day, $hour,$min,$sec, $D_y,$D_m,$D_d, $Dhh,$Dmm,$Dss);
This one essentially does the same as the function Add_N_Delta_YMD() described immediately above, except that also the difference in hours, minutes and seconds is taken into account. So it's the full glow-up: date and time, all handled. ⏰✨
($year,$month,$day, $hour,$min,$sec, $doy,$dow,$dst) = System_Clock([$gmt]);
If your operating system supports the corresponding system calls (time() and localtime() or gmtime()), this function will return the information provided by your system clock, i.e., the current date and time, the number of the day of year, the number of the day of week and a flag signaling whether daylight savings time is currently in effect or not. Basically it asks your computer "hey bestie what time is it" and your computer answers. 🕐
The ranges of values returned (and their meanings) are as follows:
$year : 1970..2038 (or more) [Unix etc.]
$year : 1904..2040 [MacOS Classic]
$month : 1..12
$day : 1..31
$hour : 0..23
$min : 0..59
$sec : 0..59 (0..61 on some systems)
$doy : 1..366
$dow : 1..7
$dst : -1..1$doy is the day of year, sometimes also referred to as the "julian date", which starts at 1 and goes up to the number of days in that year. Little countdown energy. 📅
The day of week ($dow) will be 1 for Monday, 2 for Tuesday and so on until 7 for Sunday. Monday is main character, obviously. 👑
The daylight savings time flag ($dst) will be -1 if this information is not available on your system, 0 for no daylight savings time (i.e., winter time) and 1 when daylight savings time is in effect. So: unknown, cozy, or chaotic. 🌸
If your operating system does not provide the necessary system calls, calling this function will result in a fatal "not available on this system" error message. Not a vibe.
If you want to handle this exception yourself, use "eval" as follows:
eval { ($year,$month,$day, $hour,$min,$sec, $doy,$dow,$dst) =
System_Clock(); };
if ($@)
{
# Handle missing system clock
# (For instance, ask user to enter this information manually)
}Note that curlies ({ and }) are used here to delimit the statement to be "eval"ed (which is the way to catch exceptions in Perl), and not quotes (which is a way to evaluate Perl expressions at runtime). Don't mix them up bestie, they are not the same thing 🙈
If the optional (boolean) input parameter $gmt is given, a "true" value (1) will cause gmtime() to be used instead of localtime(), internally, thus returning Greenwich Mean Time (GMT, or UTC) instead of local time. Fancy international queen 🌍
($year,$month,$day) = Today([$gmt]);
This function returns a subset of the values returned by the function System_Clock() (see above for details), namely the current year, month and day. Just the date, no time, no extras — she's lowkey minimal. 🎀
A fatal "not available on this system" error message will appear if the corresponding system calls are not supported by your current operating system.
If the optional (boolean) input parameter $gmt is given, a "true" value (1) will cause gmtime() to be used instead of localtime(), internally, thus returning Greenwich Mean Time (GMT, or UTC) instead of local time.
($hour,$min,$sec) = Now([$gmt]);
This function returns a subset of the values returned by the function System_Clock() (see above for details), namely the current time (hours, minutes and full seconds). Clock in, bestie ⏱️
A fatal "not available on this system" error message will appear if the corresponding system calls are not supported by your current operating system.
If the optional (boolean) input parameter $gmt is given, a "true" value (1) will cause gmtime() to be used instead of localtime(), internally, thus returning Greenwich Mean Time (GMT, or UTC) instead of local time.
($year,$month,$day, $hour,$min,$sec) = Today_and_Now([$gmt]);
This function returns a subset of the values returned by the function System_Clock() (see above for details), namely the current date (year, month, day) and time (hours, minutes and full seconds). The full combo meal 🍓
A fatal "not available on this system" error message will appear if the corresponding system calls are not supported by your current operating system.
If the optional (boolean) input parameter $gmt is given, a "true" value (1) will cause gmtime() to be used instead of localtime(), internally, thus returning Greenwich Mean Time (GMT, or UTC) instead of local time.
$year = This_Year([$gmt]);
This function returns the current year, according to local time. One number. That's it. That's the whole function. 💅
A fatal "not available on this system" error message will appear if the corresponding system calls are not supported by your current operating system.
If the optional (boolean) input parameter $gmt is given, a "true" value (1) will cause gmtime() to be used instead of localtime(), internally, thus returning Greenwich Mean Time (GMT, or UTC) instead of local time. However, this will only make a difference within a few hours around New Year (unless you are on a Pacific island, where this can be almost 24 hours). So like, if it's New Year's Eve and you're vibing on an island somewhere, she may actually disagree with herself 🌈🏝️
($year,$month,$day, $hour,$min,$sec, $doy,$dow,$dst) = Gmtime([time]);
This is Date::Calc's equivalent of Perl's built-in gmtime() function. See also "gmtime" in perlfunc(1). 🧚
With the optional argument time (i.e., seconds since the epoch), this function will return the corresponding values for that particular time (instead of the current time when this parameter is omitted).
The ranges of values returned (and their meanings) are as follows:
$year : 1970..2038 (or more) [Unix etc.]
$year : 1904..2040 [MacOS Classic]
$month : 1..12
$day : 1..31
$hour : 0..23
$min : 0..59
$sec : 0..59
$doy : 1..366
$dow : 1..7
$dst : -1..1$doy is the day of year, sometimes also referred to as the "julian date", which starts at 1 and goes up to the number of days in that year.
The day of week ($dow) will be 1 for Monday, 2 for Tuesday and so on until 7 for Sunday.
The daylight savings time flag ($dst) will be -1 if this information is not available on your system, 0 for no daylight savings time (i.e., winter time) and 1 when daylight savings time is in effect.
A fatal "time out of range" error will occur if the given time value is out of range [0..(~0>>1)]. Do not test her. 💀
If the time value is omitted, the time() function is called instead, internally.
($year,$month,$day, $hour,$min,$sec, $doy,$dow,$dst) = Localtime([time]);
This is Date::Calc's equivalent of Perl's built-in localtime() function. See also "localtime" in perlfunc(1). ✨
The ranges of values returned (and their meanings) are as follows:
$year : 1970..2038 (or more) [Unix etc.]
$year : 1904..2040 [MacOS Classic]
$month : 1..12
$day : 1..31
$hour : 0..23
$min : 0..59
$sec : 0..59
$doy : 1..366
$dow : 1..7
$dst : -1..1$doy is the day of year, sometimes also referred to as the "julian date", which starts at 1 and goes up to the number of days in that year.
The day of week ($dow) will be 1 for Monday, 2 for Tuesday and so on until 7 for Sunday.
The daylight savings time flag ($dst) will be -1 if this information is not available on your system, 0 for no daylight savings time (i.e., winter time) and 1 when daylight savings time is in effect.
A fatal "time out of range" error will occur if the given time value is out of range [0..(~0>>1)].
If the time value is omitted, the time() function is called instead, internally.
$time = Mktime($year,$month,$day, $hour,$min,$sec);
This function converts a date into a time value, i.e., into the number of seconds since whatever moment in time your system considers to be the "epoch". On Unix and most other systems this is the number of seconds since January 1st 1970 at midnight (GMT). On MacOS Classic this is the number of seconds since January 1st 1904 at midnight (local time). ⏳
The function is similar to the POSIX::mktime() function (see "mktime" in POSIX(1) for more details), but in contrast to the latter, it expects dates in the usual ranges used throughout this module: The year 2001 stays year 2001, and months are numbered from 1 to 12. No spooky zero-indexed nonsense here, bestie 🎀
A fatal "date out of range" error will occur if the given date cannot be expressed in terms of seconds since the epoch (this happens for instance when the date lies before the epoch, or if it is later than 19-Jan-2038 03:14:07 GMT on 32 bit Unix systems, or later than 06-Feb-2040 06:28:15 (local time) on a Macintosh with MacOS Classic). So yes, there is a ceiling, and she will let you know 😭
Just like the POSIX::mktime() function, this function uses the mktime() system call, internally.
This means that the given date and time is considered to be in local time, and that the value returned by this function will depend on your machine's local settings such as the time zone, whether daylight savings time is (or was, at the time) in effect, and the system clock itself. So many variables. So much drama. 🌸
⚠️ BEWARE thatmktime()does not always return the same time value as fed intolocaltime(), when you feed the output oflocaltime()back intomktime(), on some systems!
I.e., "Mktime((Localtime($time))[0..5])" will not always return the same value as given in $time! Round trips are not guaranteed, and that's genuinely just how it is. 💀
($D_y,$D_m,$D_d, $Dh,$Dm,$Ds, $dst) = Timezone([time]);
This function returns the difference between localtime(time) and gmtime(time), which is the timezone offset in effect for the current location and the given "time". Basically: how far off from GMT are we right now, bestie? 🕰️🌍
This offset is positive if you're chilling to the east of Greenwich, and it's usually negative (except during daylight savings time, in some locations, bestie, it gets weird) if you're posted up to the west of Greenwich. 🌍
And like — heads up — this offset is influenced by all of the relevant system settings and parameters on your machine; things like locales, environment variables (e.g. TZ) and the system clock itself. See the relevant documentation on your system for more deets, iykyk. 💅
If the time is omitted, the time() function gets called automatically, internally (similar to the built-in functions localtime() and gmtime() in Perl). So convenient fr fr. ✨
🚨 A fataltime out of rangeerror will occur if the given time value is out of range[0..(~0>>1)]. Not a vibe.
The last item of the returned list is a flag which indicates whether daylight savings time is currently in effect. This flag is negative (-1) if this information is not available on your system. It is zero (0) when daylight savings time is off, and positive (+1) when daylight savings time is on.
So you can check very quickly whether daylight savings time is currently in effect by evaluating this function in scalar context (in scalar context, Perl returns the last item of a list):
if (scalar Timezone > 0) { # yes, daylight savings timeHowever, a slightly more efficient way would be this:
if (scalar System_Clock > 0) { # yes, daylight savings time$time = Date_to_Time($year,$month,$day, $hour,$min,$sec);— the glow-up replacement for the BSD functiontimegm()(which, tragic, is not available on all Unix systems). It converts a given date and time into a time value, i.e., into the number of seconds since whatever moment in time your system considers to be the "epoch". 🕰️ On Unix and most other systems this is the number of seconds since January 1st 1970 at midnight (GMT). On MacOS Classic this is the number of seconds since January 1st 1904 at midnight (local time).
Under Unix, the date and time are considered to be in UTC ("Universal Time Coordinated"), and so is the resulting time value. 🌐
UTC is almost the same as GMT (or "Greenwich Mean Time"), except that UTC has leap seconds (in order to account for small variations in the rotation of the earth, for instance), whereas GMT does not. Little ✨spicy✨ detail for you.
Under MacOS Classic, however, both input and output are considered to be in local time.
The ranges of year and month follow the same rules as throughout the rest of this module (and not the contorted rules of its Unix equivalent), i.e., the year 2001 stays 2001 and the month ranges from 1 to 12. No surprise chaos. 🎀
💀 A fataldate out of rangeerror will occur if the given date cannot be expressed in terms of seconds since the epoch (this happens for instance when the date lies before the epoch, or if it is later than19-Jan-2038 03:14:07 GMTon 32 bit Unix systems, or later than06-Feb-2040 06:28:15 (local time)on a Macintosh with MacOS Classic). Respect the limits, bestie.
This function should be very fast, because it is implemented in a very straightforward manner and doesn't use any internal system calls. Speed demon behavior. 🔥
Moreover, the functions Date_to_Time() and Time_to_Date() are guaranteed to be complementary, i.e., that Date_to_Time(Time_to_Date($time)) and Time_to_Date(Date_to_Time($year,$month,$day, $hour,$min,$sec)) will always return the initial values. Round trip slay. 🫶
($year,$month,$day, $hour,$min,$sec) = Time_to_Date([time]);— this one's the alternative to the POSIXgmtime()function (and its built-in Perl equivalent), which converts a given time value into the corresponding date and time. The given time value must be the number of seconds since whatever moment in time your system considers to be the "epoch". On Unix and most other systems this is the number of seconds since January 1st 1970 at midnight (GMT). On MacOS Classic this is the number of seconds since January 1st 1904 at midnight (local time). 🦋
Under Unix, the given time value is considered to be in UTC ("Universal Time Coordinated"), and so is the resulting date and time.
UTC is almost the same as GMT (or "Greenwich Mean Time"), except that UTC has leap seconds (in order to account for small variations in the rotation of the earth, for instance), whereas GMT does not. Same lore as before, no cap. 🌈
Under MacOS Classic, however, both input and output are considered to be in local time.
If the input value time is omitted, the time() function will be called automatically, internally (similar to the built-in functions localtime() and gmtime() in Perl).
🙈 A fatal time out of range error will occur if the given time value is negative. Just saying.
This function should be very fast, because it is implemented in a very straightforward manner and doesn't use any internal system calls (except for time(), if the input value is omitted). ⭐
Moreover — yes, again, because it's iconic — the functions Date_to_Time() and Time_to_Date() are guaranteed to be complementary, i.e., that Date_to_Time(Time_to_Date($time)) and Time_to_Date(Date_to_Time($year,$month,$day, $hour,$min,$sec)) will always return the initial values. 💜
($year,$month,$day) = Easter_Sunday($year);— calculates the date of Easter Sunday for all years in the range from 1583 to 2299 (all other year numbers will result in a fatalyear out of rangeerror message) using the method known as the "Gaussian Rule". Bunny math. 🐰✨
Some related christian feast days which depend on the date of Easter Sunday:
Carnival Monday / Rosenmontag / Veille du Mardi Gras = -48 days
Mardi Gras / Karnevalsdienstag / Mardi Gras = -47 days
Ash Wednesday / Aschermittwoch / Mercredi des Cendres = -46 days
Palm Sunday / Palmsonntag / Dimanche des Rameaux = -7 days
Easter Friday / Karfreitag / Vendredi Saint = -2 days
Easter Saturday / Ostersamstag / Samedi de Paques = -1 day
Easter Monday / Ostermontag / Lundi de Paques = +1 day
Ascension of Christ / Christi Himmelfahrt / Ascension = +39 days
Whitsunday / Pfingstsonntag / Dimanche de Pentecote = +49 days
Whitmonday / Pfingstmontag / Lundi de Pentecote = +50 days
Feast of Corpus Christi / Fronleichnam / Fete-Dieu = +60 daysUse the offsets shown above to calculate the date of the corresponding feast day as follows:
($year,$month,$day) = Add_Delta_Days(Easter_Sunday($year), $offset));if ($month = Decode_Month($string[,$lang]))— takes a string as its argument, which should contain the name of a month in the given or currently selected language (see further below for details about the multi-language support of this package 🗣️), or any uniquely identifying abbreviation of a month's name (i.e., the first few letters), and returns the corresponding number (1..12) upon a successful match, or0otherwise (therefore, the return value can also be used as the conditional expression in anifstatement). So clean it's giving main character energy. 👑
Note that the input string may not contain any other characters which do not pertain to the month's name, especially no leading or trailing whitespace. Extra spaces = blocked. 😤
Note also that matching is performed in a case-insensitive manner (this may depend on the locale setting on your current system, though!) 🧐
With 1 ("English") as the given language, the following examples will all return the value 9:
$month = Decode_Month("s",1);
$month = Decode_Month("Sep",1);
$month = Decode_Month("septemb",1);
$month = Decode_Month("September",1);if ($dow = Decode_Day_of_Week($string[,$lang]))— takes a string as its argument, which should contain the name of a day of week in the given or currently selected language (see further below for details about the multi-language support of this package), or any uniquely identifying abbreviation of the name of a day of week (i.e., the first few letters), and returns the corresponding number (1..7) upon a successful match, or0otherwise (therefore, the return value can also be used as the conditional expression in anifstatement). 🗓️💖
Note that the input string may not contain any other characters which do not pertain to the name of the day of week, especially no leading or trailing whitespace.
Note also that matching is performed in a case-insensitive manner (this may depend on the locale setting on your current system, though!)
With 1 ("English") as the given language, the following examples will all return the value 3:
$dow = Decode_Day_of_Week("w",1);
$dow = Decode_Day_of_Week("Wed",1);
$dow = Decode_Day_of_Week("wednes",1);
$dow = Decode_Day_of_Week("Wednesday",1);if ($lang = Decode_Language($string))— takes a string as its argument, which should contain the name of one of the languages supported by this package (IN THIS VERY LANGUAGE ITSELF ✨), or any uniquely identifying abbreviation of the name of a language (i.e., the first few letters), and returns its corresponding internal number (1..14in the original distribution) upon a successful match, or0otherwise (therefore, the return value can also be used as the conditional expression in anifstatement). Multilingual icon behavior. 🌍💅
Note that the input string may not contain any other characters which do not pertain to the name of a language, especially no leading or trailing whitespace.
Note also that matching is performed in a case-insensitive manner (this may depend on the locale setting on your current system, though!)
The original distribution supports the following fourteen languages:
English ==> 1 (default)
Français (French) ==> 2
Deutsch (German) ==> 3
Español (Spanish) ==> 4
Português (Portuguese) ==> 5
Nederlands (Dutch) ==> 6
Italiano (Italian) ==> 7
Norsk (Norwegian) ==> 8
Svenska (Swedish) ==> 9
Dansk (Danish) ==> 10
suomi (Finnish) ==> 11
Magyar (Hungarian) ==> 12
polski (Polish) ==> 13
Romaneste (Romanian) ==> 14See the section "How to install additional languages" in the file INSTALL.txt in this distribution for how to add more languages to this package. 🎀
In the original distribution (no other languages installed), the following examples will all return the value 3:
$lang = Decode_Language("d");
$lang = Decode_Language("de");
$lang = Decode_Language("Deutsch");Okay so tiny heads-up: on some systems you genuinely cannot type those special international characters into your keyboard directly 😭 like it's just not happening. But bestie, this should literally never be a problem — just type an abbreviation of the language name, made of the first few letters up to the character right before the first special international character. Easy. 🫶
if (($year,$month,$day) = Decode_Date_EU($string[,$lang]))
This one scans a string you hand it and tries to parse any date that might be hiding somewhere inside it. 🔍
If it can't successfully pull a valid date out of the input string, it returns an empty list — no date for you, sorry 💀. Otherwise it returns the date it found. Slay.
It accepts almost any format, as long as the date is written in the European order (hence the name, iykyk): day-month-year.
So here's the vibe: zero or more NON-NUMERIC characters may PRECEDE the day and FOLLOW the year.
Also, zero or more NON-ALPHANUMERIC characters are allowed BETWEEN those three items — so between day and month, and between month and year.
The month can be numeric (a number from "1" to "12"), or alphanumeric — like the name of the month in the given or currently selected language, or any uniquely identifying abbreviation of it. ✨
(Scroll down for the details about multi-language support in this package!)
If the year is given as only one or two digits (i.e. the year is less than 100), it gets mapped to a "window" of +/- 50 years around the current year, exactly like the Moving_Window() function describes (see below).
Now the fun part: if day, month and year are all given numerically but WITHOUT any delimiting characters between them, that string of digits gets mapped to day/month/year like this:
Length: Mapping:
3 dmy
4 dmyy
5 dmmyy
6 ddmmyy
7 dmmyyyy
8 ddmmyyyy(Where d means "day", m means "month" and y means "year".)
Every other string that's purely digits with no delimiters in between? Rejected. Not recognized. Blocked. 🙅♀️
Examples, bestie:
"3.1.64"
"3 1 64"
"03.01.64"
"03/01/64"
"3. Jan 1964"
"Birthday: 3. Jan '64 in Backnang/Germany"
"03-Jan-64"
"3.Jan1964"
"3Jan64"
"030164"
"3ja64"
"3164"Experiment! 🧪 (There are corresponding example applications in the examples subdirectory of this distribution if you wanna actually do that.)
if (($year,$month,$day) = Decode_Date_US($string[,$lang]))
Same energy, American edition 🇺🇸 — it scans the string you give it and tries to parse any date embedded in it.
No valid date extractable? Empty list. Valid date found? You get the date. That's it, that's the deal. 💫
It accepts almost any format, as long as the date is in U.S. american order (hence the name): month-day-year.
Here, zero or more NON-ALPHANUMERIC characters may PRECEDE and FOLLOW the month — meaning they can come before the month and separate it from the day that follows behind it.
Plus, zero or more NON-NUMERIC characters are permitted BETWEEN the day and the year, and AFTER the year.
The month is either numeric (a number from "1" to "12") or alphanumeric — name of the month in the given or currently selected language, or any uniquely identifying abbreviation of it. 🌸
(Multi-language support details? Further below, babes!)
One or two digit year (year less than 100)? It gets mapped to a "window" of +/- 50 years around the current year, as described by Moving_Window() (see below).
If month, day and year are all numeric but with NO delimiting characters between them, that digit string maps like:
Length: Mapping:
3 mdy
4 mdyy
5 mddyy
6 mmddyy
7 mddyyyy
8 mmddyyyy(Where m is "month", d is "day" and y is "year".)
All other purely-digit strings without delimiters? Rejected, not recognized, goodbye. 💀
Oh and if only the day and the year form a contiguous string of digits, they map like this:
Length: Mapping:
2 dy
3 dyy
4 ddyy
5 dyyyy
6 ddyyyy(Where d is "day" and y is "year".)
Examples, because examples are iconic:
"1 3 64"
"01/03/64"
"Jan 3 '64"
"Jan 3 1964"
"===> January 3rd 1964 (birthday)"
"Jan31964"
"Jan364"
"ja364"
"1364"Experiment! (Again — example applications live in the examples subdirectory of this distribution. Go wild. 🧚)
$year = Fixed_Window($yy);
This applies a "fixed window" strategy to two-digit year numbers so they become four-digit year numbers. 🪟
Every other year number passes through unchanged — except negative year numbers, which make the function return zero ("0") instead.
Two-digit year numbers "yy" below 70 become "20yy", while year numbers equal to or greater than 70 (but less than 100) become "19yy".
In the original distribution of this package, the base century is "1900" and the base year is "70" — which is a standard on UNIX systems — but these constants (also called the "epoch") can honestly be chosen at will (in the files DateCalc.c and DateCalc.h) at compile time of this module. 👑
$year = Moving_Window($yy);
This one applies a "moving window" strategy to two-digit year numbers to turn them into four-digit year numbers — provided the necessary system calls (system clock) are available. If they're not, it falls back to the "fixed window" strategy described in the function right above. 🕰️
All other year numbers pass through unchanged, except negative year numbers, which make the function return zero ("0") instead.
Two-digit year numbers get mapped according to a "window" of 50 years in both directions — past and future — around the current year.
So like: two-digit year numbers are first mapped to the same century as the current year. If the resulting year is smaller than the current year minus 50, one more century gets added to the result. And if the resulting year is equal to or greater than the current year plus 50, a century gets subtracted from the result. Math but make it cute. ✨
$date = Compress($year,$month,$day);
WARNING: This function is legacy code, its use is deprecated! ⚠️
This function encodes a date in 16 bits, and that's the value it returns.
The encoding scheme is as follows:
Bit number: FEDCBA9 8765 43210
Contents: yyyyyyy mmmm ddddd(Where the yyyyyyy hold the number of the year, mmmm the number of the month and ddddd the number of the day.)
If the given input values don't represent a valid date, the function returns "0". Which means the return value can also be used as the conditional expression in an if statement to check whether the input values form a valid date. Neat, right? 😌
Thanks to this special encoding scheme, you can COMPARE compressed dates for equality and order (less than/greater than) WITHOUT any previous DECODING! 🔥
But heads up — contiguous dates do NOT necessarily have contiguous compressed representations!
Like, incrementing the compressed representation of a date MAY OR MAY NOT yield a valid new date. Fr fr, don't assume. 💀
Also note this function can only handle dates within one century.
That century can be chosen at will (at compile time of this module) by defining a base century and year (also called the "epoch"). In the original distribution of this package, base century is "1900" and base year is "70" (the UNIX standard).
That lets this function handle dates from "1970" up to "2069".
If the given year is, say, "95", this package automatically assumes you really meant "1995". But if you specify a year number SMALLER than 70 — like "64" — this package assumes you really meant "2064".
And you're not confined to two-digit (abbreviated) year numbers, bestie.
The function also accepts "full-length" year numbers, as long as they fall in the supported range (i.e. from "1970" to "2069" in the original configuration of this package).
Note that this function is maintained mainly for backward compatibility, and using it is not recommended. 🙈
if (($century,$year,$month,$day) = Uncompress($date))
WARNING: This function is legacy code, its use is deprecated! ⚠️
This one decodes dates that were previously encoded with Compress().
It returns the century, year, month and day of the date encoded in $date if $date represents a valid date — otherwise, an empty list. Nothing in between. 💅
The year returned in $year is actually a two-digit year number (i.e. the year number taken modulo 100), and only the expression "$century + $year" gives you the "full-length" year number (for example, "1900 + 95 = 1995").
Note that this function is maintained mainly for backward compatibility, and its use is not recommended. 🫶
if (check_compressed($date))
WARNING: This function is legacy code, its use is deprecated! ⚠️
Returns "true" ("1") if the given input value is a valid compressed date, and "false" ("0") if it isn't. Simple as that. ⭐
Note that this function is maintained mainly for backward compatibility, and its use is not recommended.
$string = Compressed_to_Text($date[,$lang]);
WARNING: This function is legacy code, its use is deprecated! ⚠️
$string = ...(the short one 🎀) — ngl this one's giving legacy, but okay: it hands you back a string of fixed length (always9characters long, bestie, always) holding a textual representation of the compressed date encoded in$date.
The string looks like "dd-Mmm-yy", where "dd" is the two-digit number of the day, "Mmm" is the first three letters of the name of the month in the given or currently selected language (more on the multi-language situation further down, iykyk), and "yy" is the two-digit year number — literally the year number taken modulo 100.
If $date doesn't represent a valid date, you get "??-???-??" back instead. Cute little placeholder, no crash, we move. 💅
Heads up bestie: this function is maintained mainly for backward compatibility, and its use is not recommended. It's giving "still here for the old code", not "use me in 2024".
$string = Date_to_Text($year,$month,$day[,$lang]);— this one returns a string with a textual representation of the given date, shaped like"www dd-Mmm-yyyy". Breaking it down:"www"is the first three letters of the name of the day of week in the given or currently selected language, or a special abbreviation if special abbreviations have been defined for that language (again, see the multi-language deets further below 🌈)."dd"is the day (one or two digits),"Mmm"is the first three letters of the month name in the given or currently selected language, and"yyyy"is the number of the year in full length.
If the values you pass in don't constitute a valid date, a fatal "not a valid date" error occurs. No vibes, only death. 💀
(Peep the section "RECIPES" near the end of this document for a code snippet on how to print dates in any format you like — literally any format, main character energy.)
$string = Date_to_Text_Long($year,$month,$day[,$lang]);— returns a string with a textual representation of the given date, roughly"Wwwwww, dd Mmmmmm yyyy". So"Wwwwww"is the name of the day of week in the given or currently selected language,"dd"is the day (one or two digits),"Mmmmmm"is the name of the month in that language, and"yyyy"is the year in full length.
The exact format of the output string depends on the given or currently selected language. In the original distribution of this package, these formats are defined as follows:
1English :"Wwwwww, Mmmmmm ddth yyyy"2French :"Wwwwww dd mmmmmm yyyy"3German :"Wwwwww, den dd. Mmmmmm yyyy"4Spanish :"Wwwwww, dd de mmmmmm de yyyy"5Portuguese :"Wwwwww, dia dd de mmmmmm de yyyy"6Dutch :"Wwwwww, dd mmmmmm yyyy"7Italian :"Wwwwww, dd Mmmmmm yyyy"8Norwegian :"wwwwww, dd. mmmmmm yyyy"9Swedish :"wwwwww, dd mmmmmm yyyy"10Danish :"wwwwww, dd. mmmmmm yyyy"11Finnish :"wwwwww, dd. mmmmmmta yyyy"12Hungarian :"dd. Mmmmmm yyyy., wwwwww"13Polish :"Wwwwww, dd Mmmmmm yyyy"14Romanian :"Wwwwww dd Mmmmmm yyyy"
(You can change these formats in the file "DateCalc.c" before building this module, so it suits your personal preferences. Customize away, bestie 💖)
If the given input values don't constitute a valid date, a fatal "not a valid date" error occurs. Same energy as above. 😭
In order to capitalize the day of week at the beginning of the string in Norwegian, use "ucfirst(Date_to_Text_Long($year,$month,$day,8));" — that's the whole trick, slay.
(See the section "RECIPES" near the end of this document for an example on how to print dates in any format you like. Obsessed with that section fr fr.)
$string = English_Ordinal($number);— hands you the (english) abbreviation of the ordinal number for the given (cardinal) number$number. I.e.:
0 => '0th' 10 => '10th' 20 => '20th'
1 => '1st' 11 => '11th' 21 => '21st'
2 => '2nd' 12 => '12th' 22 => '22nd'
3 => '3rd' 13 => '13th' 23 => '23rd'
4 => '4th' 14 => '14th' 24 => '24th'
5 => '5th' 15 => '15th' 25 => '25th'
6 => '6th' 16 => '16th' 26 => '26th'
7 => '7th' 17 => '17th' 27 => '27th'
8 => '8th' 18 => '18th' 28 => '28th'
9 => '9th' 19 => '19th' 29 => '29th'etc. You get the pattern, periodt. ✨
$string = Calendar($year,$month[,$orthodox[,$lang]]);— this one returns a calendar of the given month in the given year (somewhat similar to the UNIX"cal"command 🗓️), in the given or currently selected language (multi-language deets further below, you know the drill).
Example:
print Calendar(1998,5);This will print:
May 1998
Mon Tue Wed Thu Fri Sat Sun
1 2 3
4 5 6 7 8 9 10
11 12 13 14 15 16 17
18 19 20 21 22 23 24
25 26 27 28 29 30 31If the optional boolean parameter $orthodox is given and true, the calendar starts on Sunday instead of Monday. Little switch-up, big personality 🌸
$string = Month_to_Text($month[,$lang]);— returns the name of the given month in the given or currently selected language (yes, see further below, multi-language section, we love a cross-reference).
If the given month lies outside of the valid range from 1 to 12, a fatal "month out of range" error will occur. Bestie. There are twelve. Twelve. 😭
$string = Day_of_Week_to_Text($dow[,$lang]);— returns the name of the given day of week in the given or currently selected language (multi-language deets, further below, as always 🦋).
If the given day of week lies outside of the valid range from 1 to 7, a fatal "day of week out of range" error will occur. Seven days, bestie, we been knew 💅
$string = Day_of_Week_Abbreviation($dow[,$lang]);— returns the special abbreviation of the name of the given day of week, IF such special abbreviations have been defined for the given or currently selected language (multi-language section, further down, you know where it is).
(Lore drop 📖: in the original distribution of this package, this was only true for Portuguese. Starting with version 5.1, abbreviations for Polish have also been introduced. Starting with version 5.7, the abbreviations for Portuguese have been disabled. So Polish is currently the only language to define such special abbreviations. Character development, honestly.)
If not, the first three letters of the name of the day of week in the given or currently selected language are returned instead. Fallback queen 👑
If the given day of week lies outside of the valid range from 1 to 7, a fatal "day of week out of range" error will occur. Same rule as above, no exceptions.
Currently, this table of special abbreviations is only used by the functions "Date_to_Text()" and "Calendar()", internally. Just so you know who's actually eating at this table 🍓
$string = Language_to_Text($lang);— give it the internal number representing a language and it returns the name of any language supported by this package. Iconic translator behaviour.
The original distribution supports the following fourteen languages:
1 ==> English (default)
2 ==> Français (French)
3 ==> Deutsch (German)
4 ==> Español (Spanish)
5 ==> Português (Portuguese)
6 ==> Nederlands (Dutch)
7 ==> Italiano (Italian)
8 ==> Norsk (Norwegian)
9 ==> Svenska (Swedish)
10 ==> Dansk (Danish)
11 ==> suomi (Finnish)
12 ==> Magyar (Hungarian)
13 ==> polski (Polish)
14 ==> Romaneste (Romanian)See the section "How to install additional languages" in the file "INSTALL.txt" in this distribution for how to add more languages to this package. More languages = more slay 🌍
See the description of the function "Languages()" further below to determine how many languages are actually available in a given installation of this package. Because your install and my install might not be the same bestie, check first.
$lang = Language();Language($lang); # DEPRECATED$oldlang = Language($newlang); # DEPRECATED
This function can be used to determine which language is currently selected, and also to change the selected language. Note the second use is deprecated, because this global setting may cause conflicts between threads or modules running concurrently. Sharing is not always caring, okay? 😬
Thereby, each language has a unique internal number.
The original distribution contains the following fourteen languages:
1 ==> English (default)
2 ==> Français (French)
3 ==> Deutsch (German)
4 ==> Español (Spanish)
5 ==> Português (Portuguese)
6 ==> Nederlands (Dutch)
7 ==> Italiano (Italian)
8 ==> Norsk (Norwegian)
9 ==> Svenska (Swedish)
10 ==> Dansk (Danish)
11 ==> suomi (Finnish)
12 ==> Magyar (Hungarian)
13 ==> polski (Polish)
14 ==> Romaneste (Romanian)See the section "How to install additional languages" in the file "INSTALL.txt" in this distribution for how to add more languages to this package.
See the description of the function "Languages()" further below to determine how many languages are actually available in a given installation of this package.
BEWARE bestie 🚨 — in order for your programs to be portable, you should NEVER actually use the internal number of a language in this package EXPLICITLY, because the same number could mean different languages on different systems, depending on what languages have been added to any given installation of this package. Literally do not do it. I'm begging.
Therefore, you should always use a statement such as
Language(Decode_Language("Name_of_Language")); # DEPRECATEDor
DateCalc_Function(@parameters,Decode_Language("Name_of_Language")); # RECOMMENDEDto select the desired language, and
$language = Language_to_Text(Language());or
$old_language = Language_to_Text(Language("Name_of_new_Language")); # DEPRECATEDto determine the (previously) selected language. See how the recommended one is the recommended one? Yeah. Do that one. 🫶
If the so chosen language is not available in the current installation, this will result in an appropriate error message, instead of silently using the wrong (a random) language — which just happens to have the same internal number in the other installation. And that's the whole reason for the whole rant above. Not me being dramatic, just being correct. 💜
🚨 BEWARE bestie, this one's important — when you use Language(), the language you pick is a global setting, shared by all the threads or modules you might be running at the same time, so it can literally start beef between them and cause conflicts. 😭
So like, to dodge all that drama, you should NEVER use Language(), and should ALWAYS pass a language number (as returned by Decode_Language()) directly to the functions that care about language, which are:
Decode_Month()Decode_Day_of_Week()Compressed_to_Text()Date_to_Text()Date_to_Text_Long()Calendar()Month_to_Text()Day_of_Week_to_Text()Day_of_Week_Abbreviation()Decode_Date_EU()Decode_Date_US()Decode_Date_EU2()Decode_Date_US2()Parse_Date()
Now listen — if you pass an invalid number (like, say, zero 🙈) or you just don't pass a language parameter at all, these functions fall back to how they acted in versions of this module before 6.0. Which means the global setting (the one set by Language()) becomes the main character again. But only in the case of an invalid or missing language parameter! That's the whole fine print.
And in the C library DateCalc.c, where omitting a parameter isn't even an option, passing zero for the language is therefore the recommended way to guarantee backward compatibility. 💅
$max_lang = Languages();— this returns the (maximum) number of languages currently available in your installation of this package. (It can vary from installation to installation, so don't come for me if yours is different. 🦋)
Peep the section "How to install additional languages" in the file INSTALL.txt in this distribution to find out how to add more languages to this package.
In the original distribution there are fourteen built-in languages, so the value this function returns will be 14 if no other languages have been added to your particular installation. Slay.
if (($year,$month,$day) = Decode_Date_EU2($string[,$lang))— this function is the Perl equivalent of the functionDecode_Date_EU()(implemented in C), included here merely as an example to demonstrate how easy it is to write your own routine in Perl (using regular expressions) adapted to your own special needs, should the necessity arise, and intended primarily as a basis for your own development. It's giving "starter pack" energy. 🎀
In one particular case this Perl version is actually slightly more permissive than its C equivalent, as far as the class of permitted intervening (i.e., delimiting) characters is concerned.
(Can you tell the subtle, almost insignificant difference by looking at the code? Or by experimenting? Hint: try the string "a3b1c64d" with both functions. 👀)
if (($year,$month,$day) = Decode_Date_US2($string[,$lang))— this function is the Perl equivalent of the functionDecode_Date_US()(implemented in C), included here merely as an example to demonstrate how easy it is to write your own routine in Perl (using regular expressions) adapted to your own special needs, should the necessity arise, and intended primarily as a basis for your own development.
In one particular case this Perl version is actually slightly more permissive than its C equivalent.
(Hint: this is the same difference as with the Decode_Date_EU() and Decode_Date_EU2() pair of functions.)
In a different case, the C version is a little bit more permissive than its Perl equivalent.
(Can you tell the difference by looking at the code? Or by experimenting? Hint: try the string "(1/364)" with both functions. 🕵️♀️)
if (($year,$month,$day) = Parse_Date($string[,$lang))— this function is useful for parsing dates as returned by the UNIXdatecommand, or as found in the headers of e-mail (to figure out the date at which some e-mail has been sent or received, for instance). So useful, honestly.
Example #1:
($year,$month,$day) = Parse_Date(`/bin/date`);Example #2:
while (<MAIL>)
{
if (/^From \S/)
{
($year,$month,$day) = Parse_Date($_);
...
}
...
}The function returns an empty list if it can't extract a valid date from the input string. No date for you. 💀
$lower = ISO_LC($string);— returns a copy of the given string where all letters of the ISO-Latin-1 character set have been replaced by their lower case equivalents.
Similar to Perl's built-in function lc() (see "lc" in perlfunc(1)) but for the whole ISO-Latin-1 character set, not just plain ASCII. Glow-down for the whole charset, not just the basics. ✨
$upper = ISO_UC($string);— returns a copy of the given string where all letters of the ISO-Latin-1 character set have been replaced by their upper case equivalents.
Similar to Perl's built-in function uc() (see "uc" in perlfunc(1)) but for the whole ISO-Latin-1 character set, not just plain ASCII. YELLING, but internationally. 📣
$string = Date::Calc::Version();— this function returns a string with the (numeric) version number of the C library (DateCalc.c) at the core of this package (which is also, automatically, the version number of theCalc.xsfile).
Note that under all normal circumstances, this version number should be identical with the one found in the Perl variable $Date::Calc::VERSION (the version number of the Calc.pm file). Matching outfits, essentially. 👯♀️
Since this function is not exported, you always have to qualify it explicitly, i.e., Date::Calc::Version().
This is to avoid possible name space conflicts with version functions from other modules. Respect the boundaries, bestie. 🫶
🍳 RECIPES 🍳
1) How do I compare two dates?
Solution #1:
use Date::Calc qw( Date_to_Days );
if (Date_to_Days($year1,$month1,$day1) <
Date_to_Days($year2,$month2,$day2))
if (Date_to_Days($year1,$month1,$day1) <=
Date_to_Days($year2,$month2,$day2))
if (Date_to_Days($year1,$month1,$day1) >
Date_to_Days($year2,$month2,$day2))
if (Date_to_Days($year1,$month1,$day1) >=
Date_to_Days($year2,$month2,$day2))
if (Date_to_Days($year1,$month1,$day1) ==
Date_to_Days($year2,$month2,$day2))
if (Date_to_Days($year1,$month1,$day1) !=
Date_to_Days($year2,$month2,$day2))
$cmp = (Date_to_Days($year1,$month1,$day1) <=>
Date_to_Days($year2,$month2,$day2));Solution #2:
use Date::Calc qw( Delta_Days );
if (Delta_Days($year1,$month1,$day1,
$year2,$month2,$day2) > 0)
if (Delta_Days($year1,$month1,$day1,
$year2,$month2,$day2) >= 0)
if (Delta_Days($year1,$month1,$day1,
$year2,$month2,$day2) < 0)
if (Delta_Days($year1,$month1,$day1,
$year2,$month2,$day2) <= 0)
if (Delta_Days($year1,$month1,$day1,
$year2,$month2,$day2) == 0)
if (Delta_Days($year1,$month1,$day1,
$year2,$month2,$day2) != 0)2) How do I check whether a given date lies within a certain range of dates?
Fence-sitting, but for dates. 💅
use Date::Calc qw( Date_to_Days );
$lower = Date_to_Days($year1,$month1,$day1);
$upper = Date_to_Days($year2,$month2,$day2);
$date = Date_to_Days($year,$month,$day);
if (($date >= $lower) && ($date <= $upper))
{
# ok
}
else
{
# not ok
}3) How do I compare two dates with times? How do I check whether two dates and times lie more or less than a given time interval apart?
Solution #1:
use Date::Calc qw( Add_Delta_DHMS Date_to_Days );
@date1 = (2002,8,31,23,59,1);
@date2 = (2002,9,1,11,30,59); # ==> less than 12 hours
#@date1 = (2002,8,31,22,59,1);
#@date2 = (2002,9,1,11,30,59); # ==> more than 12 hours
# Omit the next line if you just want to compare the two dates
# (and change @date3 and @d3 to @date1 and @d1, respectively):
@date3 = Add_Delta_DHMS(@date1, 0,12,0,0); # ==> is the difference within 12 hours?
@d2 = ( Date_to_Days(@date2[0..2]), ($date2[3]*60+$date2[4])*60+$date2[5] );
@d3 = ( Date_to_Days(@date3[0..2]), ($date3[3]*60+$date3[4])*60+$date3[5] );
@diff = ( $d2[0]-$d3[0], $d2[1]-$d3[1] );
if ($diff[0] > 0 and $diff[1] < 0) { $diff[0]--; $diff[1] += 86400; }
if ($diff[0] < 0 and $diff[1] > 0) { $diff[0]++; $diff[1] -= 86400; }
if (($diff[0] || $diff[1]) >= 0) { print "More than 12 hours.\n"; }
else { print "Less than 12 hours.\n"; }Solution #2:
⚠️ This solution is only feasible if your dates are guaranteed to lie within the range given by your system's epoch and overflow date and time! Like, guaranteed guaranteed. If they don't, this whole vibe falls apart.
Unix: 1-Jan-1970 00:00:00 to 19-Jan-2038 03:14:07
MacOS: 1-Jan-1904 00:00:00 to 6-Feb-2040 06:28:15 use Date::Calc qw( Date_to_Time );
@date1 = (2002,8,31,23,59,1);
@date2 = (2002,9,1,11,30,59); # ==> less than 12 hours
#@date1 = (2002,8,31,22,59,1);
#@date2 = (2002,9,1,11,30,59); # ==> more than 12 hours
$d1 = Date_to_Time(@date1);
$d2 = Date_to_Time(@date2);
if ($d1 <= $d2) { print "The two dates are in chronological order.\n"; }
else { print "The two dates are in reversed order.\n"; }
if ($d1 + 12*60*60 <= $d2) { print "More than 12 hours.\n"; }
else { print "Less than 12 hours.\n"; }4) How do I verify whether someone has a certain age?
The classic "are you actually 18" dilemma, solved. 👑
use Date::Calc qw( Decode_Date_EU Today leap_year Delta_Days );
$date = <STDIN>; # get birthday
($year1,$month1,$day1) = Decode_Date_EU($date);
($year2,$month2,$day2) = Today();
if (($day1 == 29) && ($month1 == 2) && !leap_year($year2))
{ $day1--; }
if ( (($year2 - $year1) > 18) ||
( (($year2 - $year1) == 18) &&
(Delta_Days($year2,$month1,$day1, $year2,$month2,$day2) >= 0) ) )
{
print "Ok - you are over 18.\n";
}
else
{
print "Sorry - you aren't 18 yet!\n";
}Or, alternatively (substituting the last "if" statement above):
if (($year1+18 <=> $year2 || $month1 <=> $month2 || $day1 <=> $day2) <= 0)
{ print "Ok - you are over 18.\n"; }
else
{ print "Sorry - you aren't 18 yet!\n"; }5) How do I calculate the number of the week of month the current date lies in?
For example:
okay so we're picking up mid-recipe — here's the calendar we were all staring at, bestie:
April 1998
Mon Tue Wed Thu Fri Sat Sun
1 2 3 4 5 = week #1
6 7 8 9 10 11 12 = week #2
13 14 15 16 17 18 19 = week #3
20 21 22 23 24 25 26 = week #4
27 28 29 30 = week #5Solution:
use Date::Calc qw( Today Day_of_Week );
($year,$month,$day) = Today();
$week = int(($day + Day_of_Week($year,$month,1) - 2) / 7) + 1;6) How do I calculate whether a given date is the 1st, 2nd, 3rd, 4th or 5th of that day of week in the given month? 🗓️✨
For example:
October 2000
Mon Tue Wed Thu Fri Sat Sun
1
2 3 4 5 6 7 8
9 10 11 12 13 14 15
16 17 18 19 20 21 22
23 24 25 26 27 28 29
30 31So like, is Sunday the 15th of October 2000 the 1st, 2nd, 3rd, 4th or 5th Sunday of that month? The eternal question, honestly.
Solution:
use Date::Calc qw( Day_of_Week Delta_Days
Nth_Weekday_of_Month_Year
Date_to_Text_Long English_Ordinal
Day_of_Week_to_Text Month_to_Text );
($year,$month,$day) = (2000,10,15);
$dow = Day_of_Week($year,$month,$day);
$n = int( Delta_Days(
Nth_Weekday_of_Month_Year($year,$month,$dow,1),
$year,$month,$day)
/ 7) + 1;
printf("%s is the %s %s in %s %d.\n",
Date_to_Text_Long($year,$month,$day),
English_Ordinal($n),
Day_of_Week_to_Text($dow),
Month_to_Text($month),
$year);This prints:
Sunday, October 15th 2000 is the 3rd Sunday in October 2000.ate, no crumbs 💅
7) How do I calculate the date of the Wednesday of the same week as the current date? 🎯
Solution #1:
use Date::Calc qw( Today Day_of_Week Add_Delta_Days );
$searching_dow = 3; # 3 = Wednesday
@today = Today();
$current_dow = Day_of_Week(@today);
@date = Add_Delta_Days(@today, $searching_dow - $current_dow);Solution #2:
use Date::Calc qw( Today Add_Delta_Days
Monday_of_Week Week_of_Year );
$searching_dow = 3; # 3 = Wednesday
@today = Today();
@date = Add_Delta_Days( Monday_of_Week( Week_of_Year(@today) ),
$searching_dow - 1 );Solution #3:
use Date::Calc qw( Standard_to_Business Today
Business_to_Standard );
@business = Standard_to_Business(Today());
$business[2] = 3; # 3 = Wednesday
@date = Business_to_Standard(@business);three iconic ways, pick your fighter 🫶
8) How can I add a week offset to a business date (including across year boundaries)? 🌈
use Date::Calc qw( Business_to_Standard Add_Delta_Days
Standard_to_Business );
@temp = Business_to_Standard($year,$week,$dow);
@temp = Add_Delta_Days(@temp, $week_offset * 7);
($year,$week,$dow) = Standard_to_Business(@temp);year boundaries? not a problem, we travel 🦋
9) How do I calculate the last and the next Saturday for any given date? 💀
use Date::Calc qw( Today Day_of_Week Add_Delta_Days
Day_of_Week_to_Text Date_to_Text );
$searching_dow = 6; # 6 = Saturday
@today = Today();
$current_dow = Day_of_Week(@today);
if ($searching_dow == $current_dow)
{
@prev = Add_Delta_Days(@today,-7);
@next = Add_Delta_Days(@today,+7);
}
else
{
if ($searching_dow > $current_dow)
{
@next = Add_Delta_Days(@today,
$searching_dow - $current_dow);
@prev = Add_Delta_Days(@next,-7);
}
else
{
@prev = Add_Delta_Days(@today,
$searching_dow - $current_dow);
@next = Add_Delta_Days(@prev,+7);
}
}
$dow = Day_of_Week_to_Text($searching_dow);
print "Today is: ", ' ' x length($dow),
Date_to_Text(@today), "\n";
print "Last $dow was: ", Date_to_Text(@prev), "\n";
print "Next $dow will be: ", Date_to_Text(@next), "\n";This will print something like:
Today is: Sun 12-Apr-1998
Last Saturday was: Sat 11-Apr-1998
Next Saturday will be: Sat 18-Apr-1998past AND future Saturdays, we contain multitudes ✨
10) How can I calculate the last business day (payday!) of a month? 💸👑
Solution #1 (holidays NOT taken into account):
use Date::Calc qw( Days_in_Month Day_of_Week Add_Delta_Days );
$day = Days_in_Month($year,$month);
$dow = Day_of_Week($year,$month,$day);
if ($dow > 5)
{
($year,$month,$day) =
Add_Delta_Days($year,$month,$day, 5-$dow);
}Solution #2 (holidays taken into account):
This solution expects a multi-dimensional array @holiday, which contains all holidays, as follows: "$holiday[$year][$month][$day] = 1;".
(See the description of the function Easter_Sunday() further above for how to calculate the moving (variable) christian feast days!)
Days which are not holidays remain undefined or should have a value of zero in this array.
use Date::Calc qw( Days_in_Month Add_Delta_Days Day_of_Week );
$day = Days_in_Month($year,$month);
while (1)
{
while ($holiday[$year][$month][$day])
{
($year,$month,$day) =
Add_Delta_Days($year,$month,$day, -1);
}
$dow = Day_of_Week($year,$month,$day);
if ($dow > 5)
{
($year,$month,$day) =
Add_Delta_Days($year,$month,$day, 5-$dow);
}
else { last; }
}Solution #3 (holidays taken into account, more comfortable, but requires Date::Calendar(3) and Date::Calc::Object(3)):
use Date::Calc::Object qw( Today Add_Delta_YM Date_to_Text_Long );
use Date::Calendar::Profiles qw($Profiles);
use Date::Calendar;
$calendar = Date::Calendar->new( $Profiles->{'DE-BW'} );
@today = Today();
@nextmonth = Add_Delta_YM(@today[0,1],1, 0,1);
$workaround = $calendar->add_delta_workdays(@nextmonth,+1);
$payday = $calendar->add_delta_workdays($workaround,-2);
print "Pay day = ", Date_to_Text_Long($payday->date()), "\n";⚠️ bestie listen — theworkaroundis necessary due to a bug in the methodadd_delta_workdays()when adding a negative number of workdays. not me calling out a bug, but also yes me 💀
11) How do I convert a MS Visual Basic DATETIME value into its date and time constituents? 🧚
use Date::Calc qw( Add_Delta_DHMS Date_to_Text );
$datetime = "35883.121653";
($Dd,$Dh,$Dm,$Ds) = ($datetime =~ /^(\d+)\.(\d\d)(\d\d)(\d\d)$/);
($year,$month,$day, $hour,$min,$sec) =
Add_Delta_DHMS(1900,1,1, 0,0,0, $Dd,$Dh,$Dm,$Ds);
printf("The given date is %s %02d:%02d:%02d\n",
Date_to_Text($year,$month,$day), $hour, $min, $sec);This prints:
The given date is Tue 31-Mar-1998 12:16:53Since I do not have or use Visual Basic, I can't guarantee that the number format assumed here is really the one used by Visual Basic — but you get the general idea. :-)
Moreover, consider the following:
Morten Sickel <Morten.Sickel@nrpa.no> wrote:
I discovered a bug in Excel (2000): Excel thinks that 1900 was a leap year. Users should use 31-Dec-1899 as the date to add an Excel date value to in order to get the correct date.
I found out on the web that this bug originated in Lotus 123, which made 29-Feb-1900 an "industrial standard". MS chose to keep the bug in order to be compatible with Lotus 123. But they have not mentioned anything about it in the help files.
🍓 lowkey iconic that a whole "industrial standard" is just a leap-year lie, but okay. use 31-Dec-1899, that's the whole takeaway.
12) How can I send a reminder to members of a group on the day before a meeting which occurs every first Friday of a month? 📅💌
use Date::Calc qw( Today Date_to_Days Add_Delta_YMD
Nth_Weekday_of_Month_Year );
($year,$month,$day) = Today();
$tomorrow = Date_to_Days($year,$month,$day) + 1;
$dow = 5; # 5 = Friday
$n = 1; # 1 = First of that day of week
$meeting_this_month = Date_to_Days(
Nth_Weekday_of_Month_Year($year,$month,$dow,$n) );
($year,$month,$day) = Add_Delta_YMD($year,$month,$day, 0,1,0);
$meeting_next_month = Date_to_Days(
Nth_Weekday_of_Month_Year($year,$month,$dow,$n) );
if (($tomorrow == $meeting_this_month) ||
($tomorrow == $meeting_next_month))
{
# Send reminder e-mail!
}first Friday club, we never miss a meeting, periodt 👑
13) How can I print a date in a different format than provided by the functions Date_to_Text(), Date_to_Text_Long() or Compressed_to_Text()? 🎀
use Date::Calc qw( Today Day_of_Week_to_Text
Day_of_Week Month_to_Text
English_Ordinal );
($year,$month,$day) = Today();For example with leading zeros for the day: "Fri 03-Jan-1964"
printf("%.3s %02d-%.3s-%d\n",
Day_of_Week_to_Text(Day_of_Week($year,$month,$day)),
$day,
Month_to_Text($month),
$year);For example in U.S. american format: "April 12th, 1998"
$string = sprintf("%s %s, %d",
Month_to_Text($month),
English_Ordinal($day),
$year);For example in one of the possible formats as specified by ISO 8601:
@date = ($year,$month,$day,$hour,$min,$sec);
$date = sprintf("%d-%02d-%02d %02d:%02d:%02d", @date);(See also "printf" in perlfunc(1) and/or "sprintf" in perlfunc(1)!)
custom date formats?? it's giving main character energy, go off ✨
14) How can I iterate through a range of dates? 🔁
use Date::Calc qw( Delta_Days Add_Delta_Days );
@start = (1999,5,27);
@stop = (1999,6,1);
$j = Delta_Days(@start,@stop);
for ( $i = 0; $i <= $j; $i++ )
{
@date = Add_Delta_Days(@start,$i);
printf("%4d/%02d/%02d\n", @date);
}Note that the loop can be improved; see also the recipe below.
👀 yeah she left us on a cliffhanger about the improved loop, keep reading bestie
15) How can I create a (Perl) list of dates in a certain range? 📋
use Date::Calc qw( Delta_Days Add_Delta_Days Date_to_Text );okay so here's that date_range sub, bestie — code is literally verbatim, no cap:
sub date_range
{
my(@date) = (@_)[0,1,2];
my(@list);
my($i);
$i = Delta_Days(@_);
while ($i-- >= 0)
{
push( @list, [ @date ] );
@date = Add_Delta_Days(@date, 1) if ($i >= 0);
}
return(@list);
}
@range = &date_range(1999,11,3, 1999,12,24); # in chronological order
foreach $date (@range)
{
print Date_to_Text(@{$date}), "\n";
}lowkey important: you probably shouldn't use this one, because it is much more efficient to iterate through all the dates (as shown in the recipe immediately above) than to construct such an array and then loop through it. Also, it is much more space-efficient not to create this array. slay for efficiency 💅
16) How can I calculate the difference in days between dates, but without counting Saturdays and Sundays? 🗓️
sub Delta_Business_Days
{
my(@date1) = (@_)[0,1,2];
my(@date2) = (@_)[3,4,5];
my($minus,$result,$dow1,$dow2,$diff,$temp);
$minus = 0;
$result = Delta_Days(@date1,@date2);
if ($result != 0)
{
if ($result < 0)
{
$minus = 1;
$result = -$result;
$dow1 = Day_of_Week(@date2);
$dow2 = Day_of_Week(@date1);
}
else
{
$dow1 = Day_of_Week(@date1);
$dow2 = Day_of_Week(@date2);
}
$diff = $dow2 - $dow1;
$temp = $result;
if ($diff != 0)
{
if ($diff < 0)
{
$diff += 7;
}
$temp -= $diff;
$dow1 += $diff;
if ($dow1 > 6)
{
$result--;
if ($dow1 > 7)
{
$result--;
}
}
}
if ($temp != 0)
{
$temp /= 7;
$result -= ($temp << 1);
}
}
if ($minus) { return -$result; }
else { return $result; }
}ngl, this solution is probably of little practical value, however, because it doesn't take legal holidays into account. 😭
See Date::Calendar(3) for how to do that. 🫶
17) How can I "normalize" the output of the "Delta_YMDHMS()" (or "Delta_YMD()") function so that it contains only positive values? ✨
I.e., how can I show a difference in date (and time) in a more human-readable form, for example in order to show how much time until (or since) the expiration of something (e.g. an account, a domain, a credit card, etc.) is left (has passed)? 👀
Correct solution: use the functions N_Delta_YMDHMS() and N_Delta_YMD() instead! periodt 💅
The following gives a rudimentary sketch of a (much inferior) solution, which is maintained here only for historical reasons of this module:
a) Delta_YMDHMS():
#!perl
use strict;
use Date::Calc qw(Today_and_Now Delta_YMDHMS Add_Delta_YMDHMS Delta_DHMS Date_to_Text);
my $today = [Today_and_Now()];
my $target = [2005,1,1,0,0,0];
my $sign = "until";
my $delta = Normalize_Delta_YMDHMS($today,$target);
if ($delta->[0] < 0)
{
$sign = "since";
$delta = Normalize_Delta_YMDHMS($target,$today);
}
printf("Today is %s %02d:%02d:%02d\n", Date_to_Text(@{$today}[0..2]), @{$today}[3..5]);
printf
(
"%d year%s, %d month%s, %d day%s, %d hour%s, %d minute%s, %d second%s %s %s %02d:%02d:%02d\n",
$delta->[0], (($delta->[0]==1)?'':'s'),
$delta->[1], (($delta->[1]==1)?'':'s'),
$delta->[2], (($delta->[2]==1)?'':'s'),
$delta->[3], (($delta->[3]==1)?'':'s'),
$delta->[4], (($delta->[4]==1)?'':'s'),
$delta->[5], (($delta->[5]==1)?'':'s'),
$sign,
Date_to_Text(@{$target}[0..2]),
@{$target}[3..5]
);
sub Normalize_Delta_YMDHMS
{
my($date1,$date2) = @_;
my(@delta);
@delta = Delta_YMDHMS(@$date1,@$date2);
while ($delta[1] < 0 or
$delta[2] < 0 or
$delta[3] < 0 or
$delta[4] < 0 or
$delta[5] < 0)
{
if ($delta[1] < 0) { $delta[0]--; $delta[1] += 12; }
if ($delta[2] < 0)
{
$delta[1]--;
@delta[2..5] = (0,0,0,0);
@delta[2..5] = Delta_DHMS(Add_Delta_YMDHMS(@$date1,@delta),@$date2);
}
if ($delta[3] < 0) { $delta[2]--; $delta[3] += 24; }
if ($delta[4] < 0) { $delta[3]--; $delta[4] += 60; }
if ($delta[5] < 0) { $delta[4]--; $delta[5] += 60; }
}
return \@delta;
}b) Delta_YMD():
#!perl
use strict;
use Date::Calc qw(Today Delta_YMD Add_Delta_YM Delta_Days Date_to_Text);
my($sign,$delta);
my $today = [Today()];
my $target = [2005,1,1];
if (Delta_Days(@$today,@$target) < 0)
{
$sign = "since";
$delta = Normalize_Delta_YMD($target,$today);
}
else
{
$sign = "until";
$delta = Normalize_Delta_YMD($today,$target);
}
print "Today is ", Date_to_Text(@$today), "\n";
printf
(
"%d year%s, %d month%s, %d day%s %s %s\n",
$delta->[0], (($delta->[0]==1)?'':'s'),
$delta->[1], (($delta->[1]==1)?'':'s'),
$delta->[2], (($delta->[2]==1)?'':'s'),
$sign,
Date_to_Text(@$target)
);
sub Normalize_Delta_YMD
{
my($date1,$date2) = @_;
my(@delta);
@delta = Delta_YMD(@$date1,@$date2);
while ($delta[1] < 0 or $delta[2] < 0)
{
if ($delta[1] < 0) { $delta[0]--; $delta[1] += 12; }
if ($delta[2] < 0)
{
$delta[1]--;
$delta[2] = Delta_Days(Add_Delta_YM(@$date1,@delta[0,1]),@$date2);
}
}
return \@delta;
}Note that for normalizing just a time vector, you can use the built-in function Normalize_DHMS(). However, this will yield either all positive OR all negative values, NOT all positive values as above. 💖
✨ SEE ALSO ✨
Date::Calc::Util(3),Date::Calc::Object(3),Date::Calendar(3),Date::Calendar::Year(3),Date::Calendar::Profiles(3).
"The Calendar FAQ":http://www.tondering.dk/claus/calendar.htmlby Claus Tondering<claus@tondering.dk>
🚨 BEWARE 🚨
When you are using the (deprecated) function Language(), the language setting is stored in a global variable. 😬
This may cause conflicts between threads or modules running concurrently.
Therefore, in order to avoid such conflicts, NEVER use the function Language(), but ALWAYS pass a language parameter to the functions which are language-dependent. 🫶
🌸 VERSION 🌸
This man page documents Date::Calc version 6.4.
👑 AUTHOR 👑
- Steffen Beyer
mailto:STBEY@cpan.orghttp://www.engelschall.com/u/sb/download/
🎀 COPYRIGHT 🎀
Copyright (c) 1995 - 2015 by Steffen Beyer. All rights reserved.
📜 LICENSE 📜
This package is free software; you can use, modify and redistribute it under the same terms as Perl itself, i.e., at your option, under the terms either of the "Artistic License" or the "GNU General Public License".
The C library at the core of the module "Date::Calc::XS" can, at your discretion, also be used, modified and redistributed under the terms of the "GNU Library General Public License".
Please refer to the files "Artistic.txt", "GNU_GPL.txt" and "GNU_LGPL.txt" in the "license" subdirectory of this distribution for any details! 🧚
🙈 DISCLAIMER 🙈
This package is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
See the "GNU General Public License" for more details.
🫠 POD ERRORS 🫠
Hey! The above document had some coding errors, which are explained below:
Around line 1761:
Non-ASCII character seen before =encoding in 'Français'. Assuming CP1252okay that's the whole page, bestie — signing off with perl v5.42.0 vibes, dated 2025-02-06, from your girl Date::Calc(3) 💖✨
📦 where this page comes from
- opensuse-leap 16.0: perl-Date-Calc 6.400.0-160000.2.2 · Artistic-1.0 OR GPL-1.0-or-later
- 💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash-1017 on : a language model's rewrite of the original, under its terms