the classicist mentioned melatonim and I have had very good results with it for years. It is cheap, available at most stores and no side affects. You won't have any groggy hung over feelings in the morning. As we get older our bodies make less and less melatonin are our sleep patterns start getting messed up. It is also a very potent antioxidant.
My wife works 24 hr shifts so she uses it alot to get her body clock reset.