Biff is a command line datetime Swiss army knife

Summary

A command line tool for datetime arithmetic, parsing, formatting and more. Dual-licensed under MIT or the UNLICENSE. The user guide should be your first stop for understanding the high level concepts that Biff deals with. Otherwise, consult biff --help or biff <sub-command> --help for more specific details. Alternatively, there is a comparison between other similar tools that might give you a quick sense of what Biff is like. Print the current time: $ biff Sat, May 10, 2025, 8:02:04 AM EDT TipIf you get output like 2025 M05 10, Mon 08:02:04 instead, that's because you likely don't have locale support support configured. That requires setting BIFF_LOCALE and using a GitHub release binary or building Biff with the locale feature enabled. Print the current time in a format of your choosing: $ biff time fmt -f rfc3339 now 2025-05-10T08:08:30.101066734-04:00 $ biff time fmt -f rfc9557 now 2025-05-10T08:08:33.420946447-04:00[America/New_York] $ biff time fmt -f '%Y-%m-%d %H:%M:%S %Z' now 2025-05-10 08:08:48 EDT Print multiple relative times in one command: $ biff time fmt -f '%c' now -1d 'next sat' 'last monday' '9pm last mon' Sat, May 10, 2025, 10:44:39 AM EDT Fri, May 9, 2025, 10:44:39 AM EDT Sat, May 17, 2025, 10:44:39 AM EDT Mon, May 5, 2025, 10:44:39 AM EDT Mon, May 5, 2025, 9:00:00 PM EDT Print the current time in another time zone, and round it the nearest 15 minute increment: $ biff time in Asia/Bangkok now | biff time round -i 15 -s minute 2025-05-10T19:15:00+07:00[Asia/Bangkok] Add a duration to the current time: $ biff time add -1w now 2025-05-03T10:34:30.819577918-04:00[America/New_York] $ biff time add '1 week, 12 hours ago' now 2025-05-02T22:34:44.114109514-04:00[America/New_York] $ biff time add 6mo now 2025-11-10T10:34:49.023321635-05:00[America/New_York] Find the duration since a date in the past and round it to the desired precision: $ biff span since 2025-01-20T12:00 2636h 1m 21s 324ms 691µs 216ns $ biff span since 2025-01-20T12:00 -l year 3mo 20d 21h 1...