My husband works nights four days a week and generally has to be awake days on the other three days, so he switches back and forth all the time. He finds that melatonin helps when he has to trigger his body to know when to sleep (especially when he's sleeping nights) and he got a prescription for provigil that he takes occasionally when he needs to be awake/alert when his body is telling him to sleep.

Since you're making the shift permanent, you might want to try melatonin about a half an hour before bedtime for just a few days. You don't want to use it too often or too much since that might inhibit natural production of it, but it may speed up the process of readjusting your body to sleeping at night.

Sarah