oh dark thirty

oh dark thirty

A non-specific time in the early morning before the sun has risen. Based on the way in which military time is said aloud. ("Oh" is a common way of saying the number 0.) Why on earth are we meeting at oh dark thirty? The only thing we should be doing at this hour is sleeping! We'll have to leave at oh dark thirty if we want to reach Las Cruces before sundown.
See also: dark, oh, thirty
Farlex Dictionary of Idioms.
See also:
  • at one time or another
  • any time means no time
  • any day
  • any old time
  • against time
  • against the clock
  • any time
  • (it's) time to run
  • anytime
  • (it's) time to push along