DATEGREP(1)

📦

version 0.4.11 · 5 versions

0.4.11 · ubuntu resolute, ubuntu stonking (latest)
0.4.5 · ubuntu jammy
0.4.10 · debian bookworm
0.4.10 · ubuntu noble
0.4.11 · debian trixie, ubuntu questing

💖 DATEGREP(1) — the `dategrep` manual, bestie edition 💖

okay so. you know grep? iconic. legendary. but what if your lines were full of dates and you wanted to filter by time instead of by text? enter dategrep, a User Command, and honestly? it's giving time-travel energy. 🕰️✨

🌸 NAME 🌸

dategrep — grep standard input for lines that match EXPRESSION.

periodt. that's the whole job. 💅

✨ SYNOPSIS ✨

dategrep [OPTION]...  EXPRESSION

🦋 DESCRIPTION 🦋

Grep standard input for lines that match EXPRESSION. no cap, that's it, that's the function.

EXPRESSION can be a date/time with an operator glued on the front: <, <=, =, >=, >, !=, <>. if you don't put an operator, it defaults to =, because self-care. those operators match lines whose date/times are older, older-equal, equal, newer-equal, newer, or not equal respectively.

EXPRESSION can also be format specifiers, infixed by the same operators and suffixed by a value, like %a="Wed" — that matches lines whose %a representation (weekday name abbreviated) is "Wed". it's giving custom vibes. 🎀

EXPRESSION can also be statements like the ones above, concatenated with && (conjunction) or || (disjunction). both can be parenthesised like usual to change precedence — and heads up, && goes over ||. yes ma'am, precedence rules apply, it's very main character. 👑

If multiple date/times show up on the same line and any one of them fulfills the criteria, the line counts as a match and gets output. one is enough. we're not gatekeeping. 🫶

Note: Operations can be specified by options (--eq, --gt, ...) as well. This serves solely as a means of convenience, e.g. the datetest tool has a similar syntax. (yes the original line break goes there, we're just keeping it cute.)

Recognized OPTIONs, coming right up:

💅 OPTIONS (well, "Recognized OPTIONs") 💅

-h, --help — Print help and exit. the "hi bestie what do you need" flag.
-V, --version — Print version and exit.
-q, --quiet — Suppress message about date/time and duration parser errors. shhh. 🤫
-i, --input-format=STRING... — Input format, can be used multiple times. Each date/time will be passed to the input format parsers in the order they are given, if a date/time can be read successfully with a given input format specifier string, that value will be used. it's like a lil lineup and the first parser that recognises the date wins. 💖
-b, --base=DT — For underspecified input use DT as a fallback to fill in missing fields. Also used for ambiguous format specifiers to position their range on the absolute time line. Must be a date/time in ISO8601 format. If omitted defaults to the current date/time. the glow-up baseline, basically. ✨
-e, --backslash-escapes — Enable interpretation of backslash escapes in the output and input format specifier strings.
-o, --only-matching — Show only the part of a line matching DATE. no context, just the match. lean. 💯
-v, --invert-match — Select non-matching lines. iconic contrarian behaviour.
--from-locale=LOCALE — Interpret dates on stdin or the command line as coming from the locale LOCALE, this would only affect month and weekday names as input formats have to be specified explicitly.
--from-zone=ZONE — Consider date/times on stdin as coming from the zone ZONE, default: UTC.
-z, --zone=ZONE — Consider date/times in EXPRESSION as coming from the zone ZONE, default: UTC.
--eq — Lines match when date/times are equal to EXPRESSION.
--ne — Lines match when date/times are not the same as EXPRESSION.
--gt — Lines match when date/times are newer than EXPRESSION.
--lt — Lines match when date/times are older than EXPRESSION.
--ge — Lines match when date/times are newer than or equal EXPRESSION.
--le — Lines match when date/times are older than or equal EXPRESSION.
--nt — Lines match when date/times are newer than or equal EXPRESSION.
--ot — Lines match when date/times are older than or equal EXPRESSION.

yes, --nt and --ot really do read the same as --ge and --le in this manual. we are not fixing it, we are reporting it. facts only. 🙈

🌈 FORMAT SPECS 🌈

Format specs in dateutils are similar to posix' strftime(). BUT — and this is the plot twist — due to a broader range of supported calendars dateutils must employ different rules. 💀

🎀 Date specs

%a — The abbreviated weekday name
%A — The full weekday name
%_a — The weekday name shortened to a single character (MTWRFAS)
%b — The abbreviated month name
%B — The full month name
%_b — The month name shortened to a single character (FGHJKMNQUVXZ)
%c — The count of the weekday within the month (range 00 to 05)
%C — The count of the weekday within the year (range 00 to 53)
%d — The day of the month, 2 digits (range 00 to 31)
%D — The day of the year, 3 digits (range 000 to 366)
%F — Equivalent to %Y-%m-%d (ymd's canonical format)
%g — ISO week date year without the century (range 00 to 99)
%G — ISO week date year including the century
%j — Equivalent to %D
%m — The month in the current calendar (range 00 to 12)
%Q — The quarter of the year (range Q1 to Q4)
%q — The number of the quarter (range 01 to 04)
%s — The number of seconds since the Epoch.
%u — The weekday as number (range 01 to 07, Sunday being 07)
%U — The week count, day of week is Sun (range 00 to 53)
%V — The ISO week count, day of week is Mon (range 01 to 53)
%w — The weekday as number (range 00 to 06, Sunday being 00)
%W — The week count, day of week is Mon (range 00 to 53)
%y — The year without a century (range 00 to 99)
%Y — The year including the century
%_y — The year shortened to a single digit
%Z — The zone offset in hours and minutes (HH:MM) with a preceding sign (+ for offsets east of UTC, - for offsets west of UTC)
%Od — The day as roman numerals
%Om — The month as roman numerals
%Oy — The two digit year as roman numerals
%OY — The year including the century as roman numerals
%rs — In time systems whose Epoch is different from the unix Epoch, this selects the number of seconds since then.
%rY — In calendars with years that don't coincide with the Gregorian years, this selects the calendar's year.
%dth — The day of the month as an ordinal number, 1st, 2nd, 3rd, etc.
%mth — The month of the year as an ordinal number, 1st, 2nd, 3rd, etc.
%db — The business day of the month (since last month's ultimo)
%dB — Number of business days until this month's ultimo

🕰️ Time specs

%H — The hour of the day using a 24h clock, 2 digits (range 00 to 23)
%I — The hour of the day using a 12h clock, 2 digits (range 01 to 12)
%M — The minute (range 00 to 59)
%N — The nanoseconds (range 000000000 to 999999999)
%p — The string AM or PM, noon is PM and midnight is AM.
%P — Like %p but in lowercase
%S — The (range 00 to 60, 60 is for leap seconds)
%T — Equivalent to %H:%M:%S

🧚 General specs

%n — A newline character
%t — A tab character
%% — A literal % character

💜 Modifiers

%O — Modifier to turn decimal numbers into Roman numerals
%r — Modifier to turn units into real units
%0 — Modifier to turn on zero prefixes
%SPC — Modifier to turn on space prefixes
%- — Modifier to turn off prefixes altogether
th — Suffix, read and print ordinal numbers
b — Suffix, treat days as business days

By design dates before 1601-01-01 are not supported. it's just built different, and that's the cutoff. 🚫

For conformity here is a list of calendar designators and their corresponding format string:

ymd %Y-%m-%d
ymcw %Y-%m-%c-%w
ywd %rY-W%V-%u
bizda %Y-%m-%db
lilian n/a
ldn n/a
julian n/a
jdn n/a
matlab n/a
mdn n/a

These designators can be used as output format string, moreover, @code{lilian}/@code{ldn} and @code{julian}/@code{jdn} can also be used as input format string.

🔥 EXAMPLES 🔥

strap in, this section EATS. 👑

$ dategrep 2012-03-01 <<EOF
2012-02-28
2012-02-29
2012-03-01
2012-03-02
EOF
2012-03-01
$

$ dategrep '<2012-03-01' <<EOF
2012-02-28
2012-02-29
2012-03-01
2012-03-02
EOF
2012-02-28
2012-02-29
$

$ dategrep \!=2012-03-01 <<EOF
2012-02-28
2012-02-29
2012-03-01
2012-03-02
EOF
2012-02-28
2012-02-29
2012-03-02
$

$ dategrep =2012-03-01 <<EOF
Feb  2012-02-28
Feb  2012-02-29     leap day
Mar  2012-03-01
Mar  2012-03-02
EOF
Mar  2012-03-01
$

$ dategrep -o \<2012-03-01 <<EOF
Feb  2012-02-28
Feb  2012-02-29     leap day
Mar  2012-03-01
Mar  2012-03-02
EOF
2012-02-28
2012-02-29
$

$ dategrep '>=12:00:00' <<EOF
fileA     11:59:58
fileB     11:59:59  leap ?
fileNOON  12:00:00  new version
fileC     12:03:12
EOF
fileNOON  12:00:00  new version
fileC     12:03:12
$

$ dategrep -o '>=12:00:00' <<EOF
fileA     11:59:58
fileB     11:59:59  leap ?
fileNOON  12:00:00  new version
fileC     12:03:12
EOF
12:00:00
12:03:12
$

$ dategrep 2012-03-01 <<EOF
2012-02-28T10:00:00
2012-02-29T10:00:00
2012-03-01T10:00:00
2012-03-02T10:00:00
EOF
2012-03-01T10:00:00
$

$ dategrep '<2012-03-01' <<EOF
2012-02-28T10:00:00
2012-02-29T10:00:00
2012-03-01T10:00:00
2012-03-02T10:00:00
EOF
2012-02-28T10:00:00
2012-02-29T10:00:00
$

$ dategrep 2012-03-01T10:00:00 <<EOF
2012-02-28T10:00:00
2012-02-29T10:00:00
2012-03-01T10:00:00
2012-03-02T10:00:00
EOF
2012-03-01T10:00:00
$

$ dategrep '<2012-03-01T14:00:00' <<EOF
2012-02-28T10:00:00
2012-02-29T10:00:00
2012-03-01T10:00:00
2012-03-02T10:00:00
EOF
2012-02-28T10:00:00
2012-02-29T10:00:00
2012-03-01T10:00:00
$

🌟 AUTHOR 🌟

Written by Sebastian Freundt <freundt@fresse.org>

😭 REPORTING BUGS 😭

Report bugs to: https://github.com/hroptatyr/dateutils/issues

🫶 SEE ALSO 🫶

The full documentation for dategrep is maintained as a Texinfo manual. If the info and dategrep programs are properly installed at your site, the command

info (dateutils)dategrep

should give you access to the complete manual. go read it, it's lore. 📖✨

and that's the whole thing bestie!! 💖 this was dateutils version 0.4.11, dated November 2025, and it was DATEGREP(1) all along. go forth and grep thy dates. slay. 💅🎀🦋

📦 where this page comes from

ubuntu resolute: dateutils 0.4.11-2 · BSD-3-Clause
ubuntu stonking: dateutils 0.4.11-2 · BSD-3-Clause
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash on 2026-11-02: a language model's rewrite of the original, under its terms