I had to go from up all night back to up all day one year. It was really difficult.

My best advice is put yourself on a routine and make your waking hours active - not just physically, but socially. The idea is to not be bored, and to end the day tired. At night, take some melatonin (I used a very VERY dark stout beer, but I also didn't know about melatonin at the time). If you can get it, go for extended release melatonin, as it's designed to keep you asleep through the night. Push the routine for a solid week, and you 'should' be okay.

Also, regarding the poll, the exact amount of time for sleep depends on the person. It's based on your rem cycle, and basically regardless of the length of time you sleep, the idea is not to wake up in anything deeper than stage 2. When you do, you wake up feeling more tired than when you went to bed. The length of time between peaks in the cycle varies though, so you kind of have to gauge it yourself.