biff
last updated: May 14, 2025
https://github.com/BurntSushi/biff
https://github.com/BurntSushi/biff/blob/master/GUIDE.md
A CLI date manipulation tool from the great BurntSushi (author of ripgrep, among other stuff).
I had written my own tool, ,time (source here), which without arguments prints the time in various formats:
$ ,time
ts seconds: 1747098407.0
ts ms: 1747098407000
Local: 2025-05-12 21:06:47 EDT
UTC: 2025-05-13 01:06:47 UTC
or if you give it an argument, it tries to parse it:
$ ,time March 12 2025
ts seconds: 1741752000.0
ts ms: 1741752000000
Local: 2025-03-12 00:00:00 EDT
UTC: 2025-03-12 04:00:00 UTC
We can express each of those in biff:
$ biff time fmt -f '%s' now
1747100661
# biff doesn't support milliseconds since the epoch, so we can
# calculate it, round it to milliseconds, then strip the ms. A
# bit awkward.
# https://github.com/BurntSushi/biff/issues/3
$ biff span until -r '1970-01-01T00Z' now |
biff span round -l ms -s ms |
sed 's/ms//'
1747246662147
# by default, biff does not try to guess your desired time locale,
# and prints a rather ugly default locale
$ biff time fmt -f '%c' now
2025 M05 14, Wed 14:20:16
# so you have to ask it specifically to use your locale via the
# BIFF_LOCALE variable
$ BIFF_LOCALE=en-US biff time fmt -f '%c' now
Wed, May 14, 2025, 2:20:13 PM EDT
# to get GMT time, you need to set the TZ variable to a timezone,
# and the locale variable for date format
$ BIFF_LOCALE=en-US TZ=etc/GMT biff time fmt -f '%c' now
Wed, May 14, 2025, 6:28:09 PM GMT
But each of them is pretty awkward, so I was initially excited to replace my tool with this one but I think I'll keep it around for now.