How do I deal with jet lag?

Shifting your body clock using light, timing and sleep discipline, and what actually helps versus what does not.

Difficulty: beginner
Time: 30 min
Read: 2 min

Short answer

Get onto local time immediately — eat and sleep by the clock at your destination, not by how you feel. Daylight is the strongest signal: seek morning light travelling east, and afternoon light travelling west.

Jet lag is your body clock being out of step with local time, and light is the main thing that resets it. The direction of travel matters because lengthening a day is easier than shortening one — which is why flying west is generally easier.

What you'll need

Eye mask and earplugs (optional)
Water (optional)

Step by step

Set your watch and your behaviour to destination time as you board.Decide immediately whether it is currently day or night where you are going, and act accordingly for the whole flight.
Use daylight deliberately, in the right direction.Travelling east, seek morning light and avoid it late. Travelling west, seek afternoon and evening light. Getting this backwards slows the adjustment.
Do not nap on arrival if it is daytime.The hardest and most important rule. If you must, twenty minutes early in the afternoon, no more.
Eat at local mealtimes even if you are not hungry.Meal timing is a secondary clock signal and it reinforces the light cue.
Stay hydrated and go easy on alcohol.Cabin air is very dry, and alcohol fragments sleep quality, which makes the adjustment harder.
Get outside and move on the first day.Daylight plus physical activity is more effective than either alone, and it makes staying awake until local bedtime achievable.
Allow roughly a day per time zone.That is the realistic rate of adjustment. Planning demanding activities on day one after a long eastward flight sets you up to fail.
Shift your schedule slightly before travelling for a long trip.An hour a day for two or three days in the direction of travel reduces the gap you have to close on arrival.

Tips

For trips of two days or fewer, it is often better to stay on home time entirely rather than adjust twice.
Melatonin is used to shift the body clock and is regulated differently in different countries. Timing matters more than dose, and it is worth taking advice.
Flying east is harder than flying west because it requires shortening a day. Plan more recovery time for eastward trips.

Common mistakes

Napping on arrival after a daytime landing — It reinforces the old rhythm and is the main reason jet lag persists for days rather than resolving.
Getting bright light at the wrong end of the day — Light shifts the clock in a direction depending on when you get it. The wrong timing actively pushes you the wrong way.
Using alcohol to sleep on a flight — It reduces sleep quality and dehydrates, so you arrive less rested than if you had not slept much at all.

Questions people ask

How long does jet lag last?

Roughly a day per time zone crossed, and generally longer travelling east than west. Using daylight correctly and refusing to nap on arrival shortens it considerably.

Should I sleep on the plane?

Only if it is night-time at your destination. If it is daytime there, stay awake — sleeping on the plane at the wrong time keeps you on your old schedule.