Jet-lag planner

Builds a general plan for the days before you fly, the travel day and the days after you arrive: your sleep times, when bright light helps and when to avoid it, and when to stop caffeine.

It follows the public-health guidance listed under Sources, and says where those sources differ.

According to the CDC, the body clock is at its low point roughly two to four hours before your usual wake time; the plan takes three hours. Bright light in the hours after that low point moves the body clock earlier, which is what flying east needs; light in the evening hours before it moves the clock later, which is what flying west needs. The plan counts the six hours on either side of the low point and shows the part that falls while you are awake.

The CDC suggests shifting sleep by one hour a day, earlier before an eastward trip and later before a westward one, over the two or three days before you travel; the plan does this for up to three days if you choose. After arrival it uses the average rates of adjustment the CDC gives: about one hour a day after flying east and one and a half hours a day after flying west.

For trips of less than two days the CDC suggests keeping to home time, and the plan says so instead.

This is general guidance, not medical advice. It does not know your health, your medicines or your schedule. Speak to a doctor or pharmacist before taking melatonin, sleeping tablets or anything else for jet lag.

People adjust at different rates, so treat the times as a starting point. For a plan fitted to your own sleep pattern and itinerary, the CDC suggests considering a jet-lag calculator.

The two sources differ on melatonin: the CDC Yellow Book discusses low doses for some travellers, while the NHS does not recommend it for jet lag because there is not enough evidence that it works.

The sources also differ on naps: the CDC suggests short naps of 20–30 minutes may help, while the NHS advises not sleeping during the day at your destination. For short trips, the CDC suggests keeping to home time for trips of less than two days; the NHS suggests it for trips of two to three days.