0-dark-hundred (uncountable)

1. (chiefly US military slang) An otherwise unspecified time of night; some time when it is dark out.
   • 1996, Richard Marcinko, John Weisman, Green Team: Rogue Warrior III, page 4:

     Which is precisely why I'd volunteered as point man on this little jaunt, prowling and growling up the unlit stairwell of a Cairo slum at 0-dark-hundred to catch my quarry napping on his bedroll.

   • 2011, Diane L. Sheridan, Don't Forget the Flippin' E: A Memoir, page 290:

     It's late, and we have to get up at 0-dark-hundred to got to Paris in the AM.

• stupid o'clock, wee small hours; see also Thesaurus:early morning

• 0-dark-thirty
• dark thirty
• oh dark hundred
• oh dark thirty
• zero dark thirty

• beer o'clock