I'm actually officially on segmented sleep now so I sleep 3 hours right when I get home from work (sometime between 6-9pm) and again from 3:00am-7:30am. If I work 9am-7pm, I sleep 8pm-11pm or so, force myself out of bed on the first alarm, and go to the gym or run on the beach. 30 minutes later, I'm awake, alive, and can do freelance / hubski / read...or get shitfaced...or both between 11pm and 3am. If I didn't go to first bed until 9 or 10pm, I usually only do a 2 hour nap instead of full sleep there and skip my workout to maximize productive time. I hate that though because I usually end up losing 30-45 minutes in wake up mode, even without my workout. Hardest part was developing the wake up on first alarm habit. I've got it nailed for first sleep but still snooze 3-5 times at 8am. It's a process. I'm WAY more productive now though. It's amazing.
I spent college: 7am wake up, buy burger at Jack in the Box because it's the only place that has the lunch menu at 7am, walk to school 8am-11am go to class 11am-2pm sleep 2pm-4pm eat lunch, study 4pm-3am mix bands in clubs/study 3am-6am sleep I don't miss it.
Yeah I was on a similar horrendous sleep cycle in college. Basically a ghetto uberman with too much drinking and 12 hour sleeps when I would crash and burn. Not healthy. The biggest issue with that too is that you are forcing your body to sleep (ie: 11am-2pm) at a time when it isn't supposed to. It takes a lot of work to force yourself to sleep during the day. Blackout curtains and removing screens from your bed only help so much. Since both my sleeps are during the night now, it wasn't hard to fall asleep instantly and get a real rest out of it. I remember sleeping 3-4 hours during the day at college and I would wake up more tired. It's all about building habits and training your body though. If you focus on cycles and routines, you can pretty much be ready for anything. Also getting into a routine for eating, what you eat, gym time, personal time, veg time, work time, etc help. Chaotic things like children and cocaine do not help this though. Since I do not currently have either, I am quite enjoying my sleep cycle now.