From time to time I get asked how to use the date command to generate a timestamp. Here is an idiot-friendly script you can post for reference in your team’s bin/ if you get interrupted about timestamp questions or have an aversion to typing phrases like “man date” (with or without a space).
All but the first one and last three produce filename-friendly strings.
A big thanks to the following folks for pointing out mistakes and suggesting useful format inclusions:
- 2013-05: Rich for the reminder to include UTC and timezoned stamps.
- 2017-10: “Hamilton and Meg” (haha!) for pointing out I had my 4 year example formats messed up and for prodding me to include a 2-year example.
- 2018-01: Autumn Gray for suggesting that I add examples of including short and long days of the week.
- 2020-09: rade noticed that I had a “Zulu” notation for UTC listed as ISO8601, which it is not, and provided a correction. I’ve specified the Z-notation UTC timestamp separately from the (now corrected) ISO8601 timestamp. Thanks, rade!
#! /bin/bash
# An overly obvious reference for most commonly requested bash timestamps
# Now all you Mac fags can stop pestering me.
cat << EOD
Format/result | Command | Output
--------------------------------+----------------------------+------------------------------
YYYY-MM-DD_hh:mm:ss | date +%F_%T | $(date +%F_%T)
YYYYMMDD_hhmmss | date +%Y%m%d_%H%M%S | $(date +%Y%m%d_%H%M%S)
YYYYMMDD_hhmmss (UTC version) | date --utc +%Y%m%d_%H%M%SZ | $(date --utc +%Y%m%d_%H%M%SZ)
YYYYMMDD_hhmmss (with local TZ) | date +%Y%m%d_%H%M%S%Z | $(date +%Y%m%d_%H%M%S%Z)
YYYYMMSShhmmss | date +%Y%m%d%H%M%S | $(date +%Y%m%d%H%M%S)
YYYYMMSShhmmssnnnnnnnnn | date +%Y%m%d%H%M%S%N | $(date +%Y%m%d%H%M%S%N)
YYMMDD_hhmmss | date +%y%m%d_%H%M%S | $(date +%y%m%d_%H%M%S)
Seconds since UNIX epoch: | date +%s | $(date +%s)
Nanoseconds only: | date +%N | $(date +%N)
Nanoseconds since UNIX epoch: | date +%s%N | $(date +%s%N)
Z-notation UTC timestamp | date --utc +%FT%TZ | $(date --utc +%FT%TZ)
Z-notation UTC timestamp + ms | date --utc +%FT%T.%3NZ | $(date --utc +%FT%T.%3NZ)
ISO8601 UTC timestamp | date --utc +%FT%T%Z | $(date --utc +%FT%T%Z)
ISO8601 UTC timestamp + ms | date --utc +%FT%T.%3N%Z | $(date --utc +%FT%T.%3N%Z)
ISO8601 Local TZ timestamp | date +%FT%T%Z | $(date +%FT%T%Z)
YYYY-MM-DD (Short day) | date +%F\(%a\) | $(date +%F\(%a\))
YYYY-MM-DD (Long day) | date +%F\(%A\) | $(date +%F\(%A\))
EODIf executed, it will produce the (obvious) output:
Format/result | Command | Output
--------------------------------+----------------------------+------------------------------
YYYY-MM-DD_hh:mm:ss | date +%F_%T | 2020-09-09_11:17:10
YYYYMMDD_hhmmss | date +%Y%m%d_%H%M%S | 20200909_111710
YYYYMMDD_hhmmss (UTC version) | date --utc +%Y%m%d_%H%M%SZ | 20200909_021710Z
YYYYMMDD_hhmmss (with local TZ) | date +%Y%m%d_%H%M%S%Z | 20200909_111710JST
YYYYMMSShhmmss | date +%Y%m%d%H%M%S | 20200909111710
YYYYMMSShhmmssnnnnnnnnn | date +%Y%m%d%H%M%S%N | 20200909111710866549239
YYMMDD_hhmmss | date +%y%m%d_%H%M%S | 200909_111710
Seconds since UNIX epoch: | date +%s | 1599617830
Nanoseconds only: | date +%N | 873291281
Nanoseconds since UNIX epoch: | date +%s%N | 1599617830874893393
Z-notation UTC timestamp | date --utc +%FT%TZ | 2020-09-09T02:17:10Z
Z-notation UTC timestamp + ms | date --utc +%FT%T.%3NZ | 2020-09-09T02:17:10.878Z
ISO8601 UTC timestamp | date --utc +%FT%T%Z | 2020-09-09T02:17:10UTC
ISO8601 UTC timestamp + ms | date --utc +%FT%T.%3N%Z | 2020-09-09T02:17:10.881UTC
ISO8601 Local TZ timestamp | date +%FT%T%Z | 2020-09-09T11:17:10JST
YYYY-MM-DD (Short day) | date +%F\(%a\) | 2020-09-09(水)
YYYY-MM-DD (Long day) | date +%F\(%A\) | 2020-09-09(水曜日)
Note that the last two, short and long day-of-week are dependent on the environment variable LANG. After setting LANG=en_US we wind up with the following:
YYYY-MM-DD (Short day) | date +%F\(%a\) | 2020-09-09(Wed)
YYYY-MM-DD (Long day) | date +%F\(%A\) | 2020-09-09(Wednesday)