Whoever suggesting OP to sleep after midnight and before dawn, should themselves worry about their sleeping habits.
Anyway, [MENTION=287925]kml420[/MENTION]: Some suggestions:
1. Don't sleep in day, no matter how sleepy you are. It will be difficult at first, but slowly your body should adapt it.
2. Start watching a series. Any series: HIMYM, Lost, Game of Thrones, Heroes, Breaking Bad, Prison break... any. Watch one episode every night before you want to sleep. Don't do marathons. At max two episodes if you are curious after any cliffhanger. Try to sleep after that, thinking about what would happen next!
Do just these two things. Works for me everytime.
Disclaimer: This might improve your sleeping habit, but could make you addictive to such show! So its your choice.