oh dark thirty

Definition

Some unspecified hour in the early morning (implying an unpleasant time to be awake).

Etymology

From U.S. military terminology, in which hours before 10:00 am are prefixed with a zero, read as "oh", as in 0530, oh five-thirty, for 5:30 am.

Example Sentences

• "I had to get up at oh dark thirty to catch a plane."