How the jet lag planner works
Your body clock runs on a roughly 24-hour rhythm and is reset mainly by light. After a flight across several time zones it stays on home time for days, which causes poor sleep, daytime tiredness and an upset stomach. The planner estimates where your body clock is each day and shows when bright light helps it shift towards destination time and when light would push it the wrong way.
East or west?
Flying east, for example from Europe to Asia, the day gets shorter and the body clock has to move earlier. This is harder: it adjusts by about one hour per day. Flying west it has to move later, which is easier, about one and a half hours per day. For eastward trips of more than nine hours the planner shifts your clock the other way round, because delaying is usually quicker.
Practical tips
If you can, start shifting your sleep by an hour a day a few days before departure. On the plane, set your watch to destination time and sleep only if it is night there. After arrival, eat at local mealtimes, get outdoor light at the recommended times and wear sunglasses when light should be avoided. Keep naps under 20–30 minutes and avoid caffeine in the six hours before bedtime.
The planner gives general guidance based on published research on circadian rhythms and is not medical advice. If you have a sleep disorder or take regular medication, ask your doctor.