How to Avoid Jet Lag: Why Flying East Is Harder

Last updated October 14, 2026 · Written by Han with AI assistance, fact-checked against official sources.

Jet lag happens when your internal body clock is out of step with the local time at your destination.

This guide is general travel information, not medical advice. If you have a health condition or take medication, ask a doctor before changing your routine or using sleep aids.

Start with the time difference

The more time zones you cross, the stronger jet lag tends to be. A trip of one or two hours usually causes little trouble, while a difference of eight hours or more can affect sleep, appetite and concentration for several days. A common rule of thumb is that adjusting takes about one day for each time zone crossed, although people vary a lot.

Check the exact difference for your travel dates, because daylight saving time may change it. For example, the gap between New York and London is four hours for a few weeks in spring and one to two weeks in autumn, and five hours the rest of the year. Use Time Compare with your departure date.

Flying east is usually harder

Most people find it harder to travel east than west. Flying east means you must fall asleep earlier than your body wants, while flying west lets you stay up a little later, which is easier for most body clocks. A flight from London to New York, which goes west, is usually easier on the body than the return flight to London.

The CDC's travel health guide puts numbers on this. The body clock runs slightly longer than 24 hours, so on average people adjust by about 1.5 hours a day after a westward flight and about 1 hour a day after an eastward one. On those averages, a six-hour trip east, such as New York to Paris in winter, takes about six days to settle, and the same trip west about four.

Before you go

• For a few days before an eastward trip, go to bed and wake up an hour earlier each day if you can. For a westward trip, shift a little later.
• Choose flights that arrive in the afternoon or evening so you can go to bed at a normal local time.
• Write your first days' schedule in local time to avoid confusion on arrival.

During the flight

• Set your watch to the destination time when you board and try to sleep when it is night there.
• Drink water and limit alcohol and heavy caffeine, which can disturb sleep.
• Stand up and move around from time to time.

After you arrive

• Use daylight. Light is the strongest signal for your body clock. Spend time outside in the morning after an eastward trip, and in the late afternoon after a westward trip.
• Keep naps short. A nap of about 20 to 30 minutes can help, while a long sleep during the day can make it harder to sleep at night.
• Follow local meal times from the first day.
• Plan important meetings and decisions for times when you are normally alert.

Plan the people at home too

Your family and colleagues are in a different time zone. Before you leave, agree on times when you can call, and check what time that is in both places so nobody is woken up. The scheduling guide explains how to find an overlap.