Well, I worked 11PM-7AM hours for about 6 months, 2-4 days a week, so for me at the time, it was my normal awake hours.
Was really nice though. I had the store to myself, and very few people came in, to the point where 2-3 hours straight were completely dead. So I got to have alone time and think my thoughts and stuff.
When not working those days, I just derped around on the internet by myself for the night, since everyone in the house was asleep.
I don't work those hours anymore, but here I am, staying up when i should be going to bed, because I'm still used to those hours. (And I genuinely like being left alone at night, since I get off work at 11PM now. I wanna relax!)