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. © 2015 Farlex, Inc, all rights reserved.
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