Jet lag happens because your body clock stays on home time after you've landed somewhere else, and it only moves an hour or so a day. You can't skip the adjustment, but you can speed it up and make it gentler: start shifting before you go, switch to local time on the plane, and use light, sleep and meals to pull your clock the right way once you arrive.
How long jet lag lasts
As a rule of thumb, allow about a day for each hour of time difference flying east, and about a day for every hour and a half flying west. East is harder, because it asks your body to fall asleep earlier, against its natural tendency to drift later; our post on why jet lag is worse flying east explains why.
| Trip | Clocks | Body clock | Days to adjust |
|---|---|---|---|
| New York → London | +5h | Earlier | About 5 |
| London → New York | −5h | Later | About 4 |
| Los Angeles → London | +8h | Earlier | About 8 |
| London → Dubai | +4h | Earlier | About 4 |
| London → Singapore | +8h | Earlier | About 8 |
| Sydney → Los Angeles | −19h | Earlier | About 5 |
| New York → Tokyo | +14h | Later | About 7 |
In January, from the jet lag calculator's rule of thumb. Body clocks take the shorter way round: 16 hours ahead is adjusted as 8 behind.
A day-by-day plan
Three days before
Shift your sleep an hour a day toward your destination: earlier if you're flying east, later if west. Move meals with it. Even two or three hours of head start takes days off the adjustment.
The day you fly
- Set your watch and phone to destination time when you board, and live by it.
- Sleep on the plane if it's night where you're going; stay awake if it's day.
- Drink water, go easy on alcohol, and eat at destination meal times.
Our guides to sleeping on a plane and red-eye flights help with the night itself.
Arrival day
- Get light at the right time. After flying east, seek morning light and avoid bright evenings. After flying west, get light in the afternoon and evening. The timing matters; see light and jet lag, and check local sunrise and sunset.
- Stay up until local bedtime, or close to it. If you must sleep, keep it under 30 minutes.
- Eat at local meal times, even if you're not hungry. Meals help set the clocks in your organs.
- Caffeine in the local morning only.
The days after
Keep the same local wake-up time every day, get outside early, keep naps short, and exercise outdoors if you can. Expect the second and third nights to be patchy; that's normal.
What about melatonin?
Melatonin, the hormone your body releases in the evening, has decent evidence for jet lag, especially after flying east across five or more time zones. It's a prescription medicine in some countries and a supplement in others. Our post on melatonin and jet lag covers the research and the cautions; ask a doctor or pharmacist first.
Short trips: don't adjust at all
For a trip of two or three days, it can be better to stay on home time: keep your sleep near home hours and book important meetings for when your body thinks it's daytime. You'll come home with no jet lag to undo.
Two worked examples
New York to London: five hours east
- Before: for three nights, go to bed and get up an hour earlier each night. By departure your body is already on something like Atlantic time.
- On board: most flights leave in the evening and land around breakfast time. Eat the meal early, then sleep as much as you can; set your watch to London time at the gate.
- Day one: get outside in the late morning and around midday, keep any nap under 30 minutes, have your last coffee by early afternoon, and aim for bed at 10 or 11 PM London time.
- Days two to five: the same wake-up time every morning, daylight early, dim evenings. Most people feel close to normal by the third or fourth day.
London to Los Angeles: eight hours west
- Before: push bedtime an hour later for two or three nights. Westward shifts are easier, so this goes quickly.
- On board: the flight usually leaves in the morning or around midday and lands in the afternoon, local time. Stay mostly awake, with at most a short nap.
- Day one: get afternoon and evening light, eat dinner at local time and stay up until at least 9 or 10 PM. Expect to wake very early the first morning; keep the room dark and stay in bed if you can.
- Days two to four: evening light and a fixed wake-up time. Westward jet lag usually clears faster, in four or five days for this trip.
Common symptoms
Trouble falling asleep or waking far too early, daytime sleepiness, poor concentration, irritability, an upset stomach and a general feeling of being unwell. They come from your organs and hormones running on home time while you live on local time, and they fade as the clocks line up. If symptoms last well beyond the adjustment time, or you travel often and find it hard every time, it's worth talking to a doctor.
Before you go
Check your trip in the jet lag calculator to see which way your clock has to move and how long it will take. And if you want to rehearse the flight, Flight turns it into a focus session at your desk, as long as the real trip.