I have a pretty loose schedule. The only days I have lectures are Monday and Friday and other than that I do freelance work...
...so I have a bad sleep schedule. Usually upwards of 3am, then I wake up at 10am...
I always try to be asleep by 1am EST since I wake up relatively early, though it's been harder and harder lately due to insomnia. The plus side is that not sleeping allows me more reading time and I've made an impressive dent in my "need to read" stack, so I guess there's that!
Usually around 1 or 2 am. When I don't have school, usually around 4 - 5 am, but on nights when I want to watch Netflix, play games, etc, whenever the sun starts to come up.