xclock

Display the time in analog or digital form. More information: https://manned.org/xclock.

• Display an analog clock:
  xclock
• Display a 24-hour digital clock with the hour and minute fields only:
  xclock -digital -brief
• Display a digital clock using an strftime format string (see strftime(3)):
  xclock -digital -strftime {{format}}
• Display a 24-hour digital clock with the hour, minute and second fields that updates every second:
  xclock -digital -strftime '%H:%M:%S' -update 1
• Display a 12-hour digital clock with the hour and minute fields only:
  xclock -digital -twelve -brief