People are often surprised by my sleep schedule, especially since it's considered to be the "opposite" of people in a similar situation as my own (Software Engineer, University student).
I need about 8 hours of sleep each night to feel my best each day. I don't set an alarm unless I go to bed late and need to get up early and haven't been getting enough sleep for some days in a row.
I'm more likely to go to sleep at regular time on weekend nights (e.g. Friday and Saturday) if I'm doing something I don't particularly enjoy (e.g. reading or writing for a class I don't want to take but have to take), rather than doing something I enjoy such as reading or doing work for a class I do enjoy.
By going to bed 9 hours before I need to be up, even if I'm in bed 20 minutes late, that still gives me an extra 40 minutes for sleep. Allowing myself an extra 20-60 minutes for sleep also allows my body to get extra sleep if it needs it, which I sometimes do.
Since I'm usually out of bed before 4:40am, I can do my morning routine and be out of the house by 5:40am. In my experience, the number of cars on the road sharply increases starting 5 minutes before 6am, so leaving at 5:40am usually means there's still empty lanes on the freeway.
By getting to my destination approximately 3 hours before anyone else does, that's nearly 3 hours of focused, uninterrupted work time.
Maybe someday I'll support all of this with data and visualizations. I have a lot of data for this, I just need some time to analyze it.