the small/early hours
the small hours (of the night)and the wee hours (of the night)
the hours immediately after midnight. The dance went on into the small hours of the night. Jim goes to bed in the wee hours and gets up at lunchtime.
Also, wee hours. The hours following midnight, as in I stayed up working through the small hours, or The parents didn't come home until the wee hours. The adjectives small and wee both refer to the low numbers of those hours (one o'clock, two o'clock, etc.). [c. 1830]
the small hoursor
the wee hours
COMMON The small hours or the wee hours is the time from one o'clock in the morning until about five or six o'clock in the morning. They were arrested in the small hours of Saturday morning. That first night back, Jennifer and I sat up in bed talking into the wee hours.