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oh dark thirty

In military time, a non-specific time in the early morning, before the sun rises. Why on earth are we meeting at oh dark thirty? That's too early to do anything besides sleep!
See also: dark, oh

be (on) the wrong side of 30/40 etc.

to be older than 30, 40 etc. I don't know his exact age but I should say he's the wrong side of fifty.
See also: 30, etc, of, side, wrong