The middle watch - The old Jewish division of the night was three watches of four hours each. They are alluded to in Exo 14:24; 1 Samuel 11:11; Psalms 63:6; Psalms 90:4; Psalms 119:148; Psalms 130:6; Lamentations 2:19. After the Jews fell under the power of the Romans, they used the Roman division of four watches of three hours each Matthew 14:25; Mark 13:35.
“The beginning” of the watch would be about eleven o’clock at night.