You sleep at 4pm and wake up at 11pm or 12am? That's a full 7-8 hours of sleep already, the usual daily requirement of the average person...
If you want to sleep at a more "normal" time, then try to keep awake until 10pm and then sleep, and wake up at much later at 6am. It's going to be hard, so I suggest you ease into it by moving your sleeping schedule an hour at a time. Try sleeping at 5pm and waking up at 1am, then the next day or two try 6pm-2am, then 7pm-3am, etc until you make it to a 10pm-6am schedule.
Not all those who wander are lost.