oh dark thirty

== English == === Alternative forms === 0-dark-thirty, oh-dark-thirty, zero dark thirty, dark thirty === 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. === Pronunciation === === Noun === oh dark thirty (idiomatic) Some unspecified hour in the early morning (implying an unpleasant time to be awake). Synonyms: crack of dawn, dark o’clock, stupid o'clock, wee small hours, see also Thesaurus:early morning ==== Related terms ==== === See also ===