A
phenomenon that happens to everyone after
long distance plane flights. If the difference between the
time zones of the
origin and the
destination is above 4 hours,
jet lag will set in.
Jet lag consists of your internal body clock screwing up completely. It thinks it is day when it is really at night. So you're basically perpetually tired. The worse thing about jet lag is that even if you do manage to get to sleep (it is like trying to fall asleep right after you get up), when you get up, it is probably at the worst possible time (9pm) and everyone else is about to go to sleep.
The worst possible scenario of jet lag is when the time difference is 12 hours. Unfortunately, my two current homes is in Ithaca, NY and Shanghai, China, and the difference is about 12 hours. It takes about a week for your body to adjust to the time change. You're basically in bed during the day and prowling around at night. Like a vampire or something.