July 25, 2026 9 min read

How to Beat Jet Lag: A Plan for Flying East or West

You cannot prevent jet lag, but you can shorten it. Move your sleep toward destination time for a few days before you fly, live on destination time from the moment you board, and use daylight at the right end of the day: morning light after flying east, evening light after flying west. Sleep specialists estimate the body clock needs about one day per time zone to catch up fully, so the plan matters most on trips of five hours or more.

What jet lag is

Jet lag is a mismatch between your internal body clock and the clock on the wall. Your circadian rhythm runs on a roughly 24-hour cycle and tells you when to feel sleepy and when to feel alert. Fly from New York to London overnight and you land at 7:00 a.m. local time while your body thinks it is 2:00 a.m. The American Academy of Sleep Medicine (AASM) classes jet lag as a circadian rhythm sleep disorder and notes it can begin after crossing as few as two time zones.

The NHS lists the main symptoms as trouble sleeping at bedtime and waking in the morning, tiredness, difficulty staying awake during the day, poor sleep quality, and problems with concentration and memory. Indigestion, nausea, constipation, appetite changes and mild anxiety can come with it.

A long flight that stays in roughly the same zone, such as London to Johannesburg, can leave you exhausted from the trip itself, but there is no clock gap for your body to close. Travel tiredness fades after a good night's sleep. Jet lag keeps returning at the same wrong hours until your rhythm has shifted.

The machinery behind this rhythm is well mapped. The 2017 Nobel Prize in Physiology or Medicine went to Jeffrey C. Hall, Michael Rosbash and Michael W. Young for discovering the molecular mechanisms that control the circadian rhythm, and the Nobel Assembly named jet lag as the everyday example of what happens when that clock and the outside world disagree.

Why the number of time zones and the direction matter

The AASM estimates that it takes about one day per time zone for the body clock to fully adjust, and it says severity depends on both the number of zones crossed and the direction of travel. Flying east is usually the harder adjustment. Australia's Better Health Channel gives the reason: most people's natural body clock runs slightly longer than 24 hours, so stretching the day (flying west) goes with the grain, while shortening it (flying east) works against it. Age matters too. Both the AASM and healthdirect note that older adults tend to adjust more slowly.

Treat the last column as a ceiling, not a sentence. Many people feel mostly normal well before their clock has fully moved, and healthdirect puts the usual adjustment at "at least 2 or 3 days". The comparison of the two directions is the subject of our post on whether jet lag is worse flying east or west.

Before you fly: shift your schedule

The NHS suggests starting to go to bed and get up earlier or later than usual, closer to the time at your destination, and getting plenty of rest before you travel. The AASM recommends making that change gradually so your sleep is already near destination time when you leave. Going east, move bedtime and wake time earlier. Going west, move them later; Better Health's example for Melbourne to London is going to sleep at 1:00 to 2:00 a.m. for the two or three nights before departure.

Here is how that looks for a New York to London trip with a 7:00 p.m. departure, shifting in one-hour steps from a usual 11:00 p.m. to 7:00 a.m. night:

Three hours of the five-hour gap are covered before you board. If your job or family makes that impossible, even one or two steps help, and sleeping well beats shifting hard: the Better Health Channel notes that a sleep debt makes jet lag worse. Set each step on the alarm clock the evening before.

Short trips are the exception. The NHS and healthdirect both suggest that for a trip of two to three days you could stay on your home schedule for eating and sleeping, so you do not have to readjust twice.

Light is the main lever

Light reaching the eyes is the strongest signal the body clock uses. The US National Institute of General Medical Sciences says light and dark have the biggest influence on circadian rhythms, ahead of meals, activity and temperature. The timing decides which way the clock moves, and healthdirect gives the rule by direction:

• After flying east: get sunshine in the early morning.
• After flying west: aim for sunlight in the evening.

In both cases keep the bedroom as dark as you can at night. The AASM adds a caution: light at the wrong point in your body's cycle can push the clock the wrong way. That matters most for light boxes and other bright light therapy, and the AASM advises talking to a sleep provider before using one. Ordinary daylight outdoors, at the times above, is the low-risk version.

Exercise fits in here as well. The AASM says some studies show moderate exercise helps adjustment, and outdoor exercise adds daylight at the same time. A morning walk after landing in London does both jobs.

On the plane

Switch your watch and phone to destination time when you board and start living on it. healthdirect suggests eating and sleeping on the plane as you would at your destination; the NHS says to try to sleep if it is night where you are going. On the New York to London example, that means trying to sleep soon after dinner, because it is already past midnight in London.

• Drink plenty of water, and walk around the cabin and stretch regularly (NHS).
• Use an eye mask and earplugs if they help you sleep (NHS).
• Keep caffeine and alcohol low. The NHS says both can make jet lag worse, and the AASM recommends avoiding them while crossing time zones.

If the time conversion on your boarding pass confuses you, our post on reading flight times across time zones walks through it, and the time zone converter does it for any date.

After landing

The NHS advice is to switch your sleep to the new time zone as quickly as possible, set an alarm so you do not oversleep in the morning, and get outside during the day. Eat meals at local times too, since they give your body another clue about the hour.

Naps are where the sources differ. The NHS says not to sleep during the day at all. healthdirect allows short naps in the first few days, no longer than 30 minutes, and recommends being awake for at least four hours before bedtime. If you nap, keep it short with a timer, and see our post on power naps for how long is long enough.

Melatonin and sleeping pills

Melatonin is the hormone your body releases in the evening as a signal for sleep. As a pill, it is regulated very differently depending on the country. In the UK it is a prescription-only medicine, and the NHS says melatonin tablets are not recommended on the NHS for jet lag because there is not enough evidence that they work. In the United States it is sold as a dietary supplement, which NCCIH points out is regulated less strictly than prescription or over-the-counter drugs; a 2023 study it cites found that 22 of 25 melatonin gummy products were inaccurately labeled.

On whether it helps, NCCIH says research suggests it may: four small studies (142 travelers in total) found melatonin may beat a placebo after eastward flights, and two studies (90 travelers) after westward flights. The AASM adds that timing matters, because melatonin taken at the wrong time can make the misalignment worse. Sleeping pills are a separate question; the NHS says they can be addictive and should be used only for a short time when symptoms are severe.

Plan it with the tools

1. Add your destination to the world clock so home time and destination time sit side by side. The current time in London, Tokyo, New York and Sydney pages also show the next clock change, which can move the gap by an hour.
2. Convert your departure and arrival times with the time zone converter, then write your arrival in destination time.
3. Set one alarm per night for the pre-flight steps, and one for the first local morning.

Coming home is a second trip with the direction reversed, so a Europe to US return is the easier westward case. Recovery timelines for both legs are in how long jet lag lasts. Before your next long flight, add the destination to the world clock and set the first of those alarms.

Frequently asked questions