How to handle a jetlag?

Symptoms

Fatigue and disorientation
Disturbed sleep
Fuzziness
Dehydration

Jetlag, one of the most common sleep disorders, is caused by an imbalance in the circadian rhythms (body clock).

Our circadian rhythms are set to work on a 24 hour cycle and can be measured by the rise and fall in body temperature and hormone levels. When travelling to a new time zone, especially eastwards, they are slow to adjust and can remain on the original cycle for several days. (NASA estimates that it takes 1 day for every one hour time zone crossed.)

Travelling East (from the UK) you should advance the body clock. The number of time zones corresponds to the number of hours you need to change. When you arrive it is better to avoid bright light to encourage the build up of melatonin to help you sleep, and take the bright light in the morning to wake you up.
Travelling West (from the UK) before you travel, you can delay the body clock by using extra light in the evening. On arrival use bright light in the afternoon and evening to postpone bedtime and then again in the morning to wake you up.