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.
#! /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)
ISO8601 UTC timestamp | date --utc +%FT%TZ | $(date --utc +%FT%TZ)
ISO8601 UTC timestamp + ms | date --utc +%FT%T.%3NZ | $(date --utc +%FT%T.%3NZ)
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\(%A\))
EOD
If executed, it will produce the (obvious) output:
Format/result | Command | Output --------------------------------+----------------------------+------------------------------ YYYY-MM-DD_hh:mm:ss | date +%F_%T | 2020-01-31_23:15:08 YYYYMMDD_hhmmss | date +%Y%m%d_%H%M%S | 20200131_231508 YYYYMMDD_hhmmss (UTC version) | date --utc +%Y%m%d_%H%M%SZ | 20200131_141508Z YYYYMMDD_hhmmss (with local TZ) | date +%Y%m%d_%H%M%S%Z | 20200131_231508JST YYYYMMSShhmmss | date +%Y%m%d%H%M%S | 20200131231508 YYYYMMSShhmmssnnnnnnnnn | date +%Y%m%d%H%M%S%N | 20200131231508163085835 YYMMDD_hhmmss | date +%y%m%d_%H%M%S | 200131_231508 Seconds since UNIX epoch: | date +%s | 1580480108 Nanoseconds only: | date +%N | 169140987 Nanoseconds since UNIX epoch: | date +%s%N | 1580480108170759606 ISO8601 UTC timestamp | date --utc +%FT%TZ | 2020-01-31T14:15:08Z ISO8601 UTC timestamp + ms | date --utc +%FT%T.%3NZ | 2020-01-31T14:15:08.175Z ISO8601 Local TZ timestamp | date +%FT%T%Z | 2020-01-31T23:15:08JST YYYY-MM-DD (Short day) | date +%F\(%a\) | 2020-01-31(金) YYYY-MM-DD (Long day) | date +%F\(%A\) | 2020-01-31(金曜日)
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\(%a\) | 2018-01-24(Wed) YYYY-MM-DD (Long day) | date +%F\(%A\) | 2018-01-24(Wednesday)