Watches means in the bible: Like the Babylonians or Greeks, the Jews divided the night into three watches. “The beginning of the watches” was sunset to 10 p.m. Lam. 2:19 The “middle watch,” 10 pm to 2 a.m. Judg. 7:19 and “morning watches,” 2 a.m. to sunrise Ex. 14:24; 1 Sam. 11:11, Luke 12:38. Four watches were used by the Romans, which is why Matt refers to their custom. 14:25, Mark 6:48; 13.35
(in Bible Dictionary)