I've always been confused about sleep needs. If I take a half-hour nap after work ('cause I'm one of those dinosaurs), I'm lying in bed awake for hours that night. You'd think I would just fall asleep a half hour later than usual.

Oddly, my internal clock is unaffected by the amount of sleep I get. If I crash at 10:00 pm or finally drift off at 2:00 am, my mental clock still wakes me up at the same time. Interesting!