The Jews divided the day, from sunrise to sunset, into twelve hours. The length of the hours varied with the length of the day; and the length of the day varied thus (approximately): —
Sun rises.
Sun sets.
21st of Adar
6 o’clock
6 o’clock = 12 hours.
21st of Sivan
5 o’clock
7 o’clock = 14 hours.
21st of Elul
6 o’clock
6 o’clock = 12 hours.
21st of Chisleu
7 o’clock
5 o’clock = 10 hours.
Twilight — before sunrise, and after sunset — would vary from three hours (an hour and a half both morning and evening) on the shortest day, to four hours on the longest day (two hours both morning and evening).