1) Not prime time 2) Predawn period 3) Very early in the morning 4) Very early morning 
Small Hours is the current late night radio show hosted by Donal Dineen on Today FM. It commenced broadcasting in 2004, following the seven-year tenure of Here Comes the Night. It is Dineen`s second radio show on Today FM, airing Monday - Thursday, 00:00 - 02:00. On 30 December 2007, The Small Hours had a two-hour radio special broadcast from the....
[n] - the hours just after midnight
noun the hours just after midnight