Melatonin is awesome. It works awesome for this:
http://en.wikipedia.org/wiki/Delayed_sleep_phase_disorder
I sometimes drink chamomile tea and I have had sleepytime. They are tasty.
Melatonin is the only thing that ever really works for me.
Without Melatonin (the first 32 years of my life ... )
Hated school every day starting in 1st grade (I had "afternoon kindergarten", which was ok.)
Worked nights/evenings starting my 16th birthday.
Worked nights/evenings through college
Worked night/sevenings until I was 21.
Then I got a day job in a help desk type setting. Worked days for about 6 months. On average was tired and usually got to sleep by 3 and then up by 8. It sucked really bad.
Once fully trained, I volunteered for overnights. I slept better, but, still messed up sleep cycle since it was a "7 on 7 off" schedule, and after having just worked a 77 hour week for my 7 on, I mucked about during my 7 off.
After that I got into 2pm to 12:30am schedule, and kept it for a couple of years. That was the best schedule/hours I'd ever had. I would kill to have those hours again. I slept well every night/morning. I went out and had fun almost every night after work. Life was awesome.
Since then, I've been working starting at 9am, (though I did do a stretch of working 6:30am-3pm ... but that was even more miserable.)
Anyhow ... without melatonin, I am horribly tired and burned out and worn out every day of the week since I am sleep deprived since laying down while awake does not count as "sleep." I sleep 3-8 or 3-7:30, and only wake up at the latest possible second to get to work on time.
With melatonin, I can take 3-4mg at midnight, and usually I'm asleep before 1am. If not, at 1am, I take another 3-4mg and am always asleep by 2am.
That gives me around 7 hours of great sleep. I've gotten my body mostly used to the hours, so I don't generally need to take the melatonin every day any more even.
So, for people who have a schedule that does not accommodate their circadian rhythm, melatonin can be a VERY powerful and magnificent life improving tool.