There isn't any fast way to reset the biological clock. But there are a few tricks to help. First of all, you need to be sure to provide the right environmental cues. That means you wake yourself up in the morning at a decent hour, and get yourself into sunlight. You eat three regular meals, at the clock appointed time. You do not take naps during the day. At night, you tuck into bed by about 9-10pm, and repeat the process the next day. Melatonin is useless as far as I'm concerned. I did a lot of flying, cross time zones and the date line while in the military. Been there, done the jet lag thing a few times. It takes about a week to feel you have sync again, though as a rule the first two or three days are the worst. The sooner you slide back into a regular day schedule, the better. For the meantime, life gets ruled by the clock and not the body cues.