i used to need about 4 hours a night, not sure when was the best time. now i am sick and need 6 hours most nights/days. as a teen i would routinely wake at about 2 am and wander the streets of new york for an hour or two before going back to bed. i work overnights now and have off and on for the past 15 years. i usually adapt well to daytime hour schedules, but end up having late nights on a regular basis; when i work overnights i usually sleep between 12pm and 2pm until i wake up, which usually is 7 or 8pm