dotfile snippets: easily list `date` formatting and format strings on macOS (and linux)
I don't like fiddling around typing out date formats when I'm working – who does? I found this snippet a while ago. Unfortunately, I don't remember where anymore. I would love to credit the person who I copied this from, so let me know if you find it!
macOS
This is a bit cheaty because it doesn't use macOS's built-in date. For uniformity, since I work on both macOS and Linux a lot, I just use GNU's tools. For example, date is provided through coreutils, which can be installed through Brew:
brew install coreutils
This should, by default, add gdate to your $PATH (all GNU commands are prefixed with g to not conflict with the built-in macOS commands).
In ~/.zshrc:
dates() {
cat << EOD
Format/result | Command | Output
------------------------------------+-----------------------------+------------------------------
YYYY-MM-DD_hh:mm:ss | gdate +%F_%T | $(gdate +%F_%T)
YYYYMMDD_hhmmss | gdate +%Y%m%d_%H%M%S | $(gdate +%Y%m%d_%H%M%S)
YYYYMMDD_hhmmss (UTC version) | gdate --utc +%Y%m%d_%H%M%SZ | $(gdate --utc +%Y%m%d_%H%M%SZ)
YYYYMMDD_hhmmss (with local TZ) | gdate +%Y%m%d_%H%M%S%Z | $(gdate +%Y%m%d_%H%M%S%Z)
YYYYMMDD_Thhmmss (with num TZ) * | gdate +%Y%m%d_T%H%M%S%z | $(gdate +%Y%m%d_T%H%M%S%z)
YYYYMMSShhmmss | gdate +%Y%m%d%H%M%S | $(gdate +%Y%m%d%H%M%S)
YYYYMMSShhmmssnnnnnnnnn | gdate +%Y%m%d%H%M%S%N | $(gdate +%Y%m%d%H%M%S%N)
YYMMDD_hhmmss | gdate +%y%m%d_%H%M%S | $(gdate +%y%m%d_%H%M%S)
Seconds since UNIX epoch: | gdate +%s | $(gdate +%s)
Nanoseconds only: | gdate +%N | $(gdate +%N)
Nanoseconds since UNIX epoch: | gdate +%s%N | $(gdate +%s%N)
ISO8601 UTC timestamp | gdate --utc +%FT%TZ | $(gdate --utc +%FT%TZ)
ISO8601 UTC timestamp + ms | gdate --utc +%FT%T.%3NZ | $(gdate --utc +%FT%T.%3NZ)
ISO8601 Local TZ timestamp | gdate +%FT%T%Z | $(gdate +%FT%T%Z)
YYYY-MM-DD (Short day) | gdate +%F\(%a\) | $(gdate +%F\(%a\))
YYYY-MM-DD (Long day) | gdate +%F\(%A\) | $(gdate +%F\(%A\))
"ISO8601"-ish timestamp + w/ | gdate +%F_T%H-%M-%S%z | $(gdate +%F_T%H-%M-%S%z)
numerical timezone | |
YYYYMMDD_hhmmss (with local TZ) | gdate +%F_T%H%M%S%z | $(gdate +%F_T%H-%M-%S%z)
numerical timezone (no dash) | |
Notes:
* use this for filenames
EOD
}
On Linux you just use date instead of gdate:
dates() {
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)
YYYYMMDD_Thhmmss (with num TZ) * | date +%Y%m%d_T%H%M%S%z | $(date +%Y%m%d_T%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\(%A\))
"ISO8601"-ish timestamp + w/ | date +%F_T%H-%M-%S%z | $(date +%F_T%H-%M-%S%z)
numerical timezone | |
YYYYMMDD_hhmmss (with local TZ) | date +%F_T%H%M%S%z | $(date +%F_T%H-%M-%S%z)
numerical timezone (no dash)
EOD
}
Example output:
Format/result | Command | Output
------------------------------------+-----------------------------+------------------------------
YYYY-MM-DD_hh:mm:ss | gdate +%F_%T | 2025-02-01_15:30:00
YYYYMMDD_hhmmss | gdate +%Y%m%d_%H%M%S | 20250201_153000
YYYYMMDD_hhmmss (UTC version) | gdate --utc +%Y%m%d_%H%M%SZ | 20250201_233000Z
YYYYMMDD_hhmmss (with local TZ) | gdate +%Y%m%d_%H%M%S%Z | 20250201_153000PST
YYYYMMDD_Thhmmss (with num TZ) * | gdate +%Y%m%d_T%H%M%S%z | 20250201_T153000-0800
YYYYMMSShhmmss | gdate +%Y%m%d%H%M%S | 20250201153000
YYYYMMSShhmmssnnnnnnnnn | gdate +%Y%m%d%H%M%S%N | 20250201153000726647000
YYMMDD_hhmmss | gdate +%y%m%d_%H%M%S | 250201_153000
Seconds since UNIX epoch: | gdate +%s | 1738452600
Nanoseconds only: | gdate +%N | 734241000
Nanoseconds since UNIX epoch: | gdate +%s%N | 1738452600737131000
ISO8601 UTC timestamp | gdate --utc +%FT%TZ | 2025-02-01T23:30:00Z
ISO8601 UTC timestamp + ms | gdate --utc +%FT%T.%3NZ | 2025-02-01T23:30:00.741Z
ISO8601 Local TZ timestamp | gdate +%FT%T%Z | 2025-02-01T15:30:00PST
YYYY-MM-DD (Short day) | gdate +%F\(%a\) | 2025-02-01(Sat)
YYYY-MM-DD (Long day) | gdate +%F\(%A\) | 2025-02-01(Saturday)
"ISO8601"-ish timestamp + w/ | gdate +%F_T%H-%M-%S%z | 2025-02-01_T15-30-00-0800
numerical timezone | |
YYYYMMDD_hhmmss (with local TZ) | gdate +%F_T%H%M%S%z | 2025-02-01_T15-30-00-0800
numerical timezone (no dash) | |
Notes:
* use this for filenames