It is actually o' dark-thirty. It is a military term refering to beinging somewhere before the sun rises
We have to go, we have PT (physical training)at 0' dark-thirty.
the thirty minutes before nightfall, or the thirty minutes after night falls.basically the 1 hour time frame as it becomes dark.
i told david the party starts at dark-thirty.
Something hicks from illinois say when they're referring to the time right after the sun sets.
Be home before darkthirty ya'll.
the hour of the day that it becomes dark so it could be a half hour before or a half hour after it gets dark
i told bobby and jonny boy to be at my house to suck some little dick at dark-thirty