I'm definitely a night owl. Naturally, when I have no commitments, I hate going to bed and can only do it when I'm very tired. So I tend to go to bed very late. Circa 2am or later in the morning, and I'll wake up at 10am at the earliest.
Edit: But I cannot get up too late, otherwise I feel like I've wasted a day. Even if I do 'waste' that day in some other way, like playing games on the computer.