When we travel across differing 'time zones' our normal rhythm is altered. The sleep disturbance and loss of ability to concentrate, as well as the irritability felt during that time is known as jet lag. Jet lag is more commonly found after long haul flights, normally over 6 hours, and where the destination has a differing time zone to the departure country.
The earth is divided into 24 time zones. If you travel from London to New York, you will need to turn your watch back by 5 hours, as New York is five time zones behind the UK. If you travel to Japan from London, you will need to turn your watch forward by nine hours instead. It is worth remembering if you travel East, your clock will go forward, whereas if you travel to the West, your clock will go back. Hence arriving in Tokyo by plane from London at bedtime, your body will feel as though it is lunchtime. It will take at least 24 hours for the body to adjust and settle back into a routine.
Reducing Jet Lag
Make sure you have plenty of sleep before your departure to compensate for any lack of sleep the body may experience once you arrive. You should also try to relax and unwind as much as possible during your journey, perhaps have a nap if possible. It would be beneficial if you can plan your landing time so it is close to bed time, so that once you land and check in, you can head straight to bed to adjust and recuperate. By the next day, you should be feeling much better and refreshed. If you are able to plan your itinerary like this, allow time upon arrival for adjustment. For example, don’t make any important plans immediately after landing. If you must keep an appointment while away, make sure you give yourself at least two full days to recover. For those with important schedules and meetings it would be worth discussing with your doctor the possible benefits of a mild sleeping tablet for 2-3 days whilst you adjust.
Some people also advise changing your watch or phone times to destination time when you get onto the plane. However, make sure you do not do this if you need to take medication at regular intervals as you may become confused. Exposure to natural light is also a good way of naturally allowing your body to adjust, as is eating local meals and gentle activity after landing.