Asking a musician friend what time his band started tonight:
(shrug) “Rock o’clock.” 
Navy Dad, Army Mom. (My mom DOES wear combat boots. Or did.)
Oh-dark-thirty. It’s usually for somewhere between four and five, with five being almost a smidge too late for oh-dark-thirty. Past midnight, because midnight is early, and occasionally as early as threeish. “What are you thinking, getting home at oh-dark-thirty?”
My daddy always said that he could have gone into the Air Force but he’d already BEEN to summer camp. 
(i keed, i keed)
heh. unfortunately, no.
i’ve just worked way too many mount comfort air shows (indianapolis) over the years. both the dive master and i are plane freaks from way back - especially ww2 vintage. in fact, we just got back from the wright-patt air museum a week ago. whatta place to ogle planes all day. that’s my sixth visit now, i think.
they have the memphis belle undergoing preservation right now!!
Actually, his parties are quite mixed – most major sexual orientations and an assortment of genders. You’d be very welcome 
I forgot one useful time: half-past. When we were at the cottage, my grandfather always used to tell us, “Now, don’t get up before half-past.” We didn’t.
Air Force vet here. Oh-Dark-Thirty and Oh-Dark-Hundred were used often. Never heard Zero-Dark-Thirty used – seems too hard to say.