Personally, 10pm. I typically only need about 7 hours of sleep to be well-rested. (Just to make up the difference, I sleep 10pm-7(:30)am on weekends.)
If you find you need 7.5 or 8 hours of sleep, you can shift the bedtime or wakeup times around, of course. This week, I've been unusually tired, so I've been doing 10pm-5:30am or 10pm-6am.
We're a place where coders share, stay up-to-date and grow their careers.
We strive for transparency and don't collect excess data.