I have insomnia, so while I try to keep my bedtime between 9 and 1, I'm often still awake around 4 or 5am. But I guess that doesn't really count as "bedtime". My sleeping pills make it (relatively) easy to regulate when I sleep, but it also means I have to keep the same hours fairly consistently. Since I have a 9:30 class this term, even if it's only one day a week, I'll probably be going to bed around 11ish every night so that the effect of my sleeping pills will have worn off by the time I need to get up and get going. If I'm really tired from lack of sleep the night before and haven't had caffeine, sometimes I'll get away with going to bed as early as 9. :x
It really sucks going to bed at 10 or 11 since I'm a night owl but you do what you gotta do.