wee small hours

From Scots wee sma' hours (first attested in 1819).

wee small hours pl (normally plural, singular wee small hours)

1. (informal) The very early morning, just after midnight, when most people are asleep.

   He worked into the wee small hours to get everything perfect for the opening day.

Within the context of a sentence, almost always used with the definite article "the", especially, or a demonstrative adjective.

• (very early morning): oh dark thirty, small hours, wee hours