How long jet lag lasts depends mostly on what you do on arrival day. One lever is strong, one is moderate, and a few decisions decide whether the adjustment takes one day or three.
Eastward is the hard direction
Most people reach Asia from Europe or the Americas by flying east. That compresses your day and asks your body clock to advance. The human clock runs slightly long by nature, so delaying it is easier than advancing it.
Expect the trip out to be harder than the trip home, and do not plan an ambitious first morning.
The strong lever: light at the right time
Daylight is the main signal your clock uses, and its timing matters more than its amount. After a large eastward shift, morning light at the destination helps you advance. Nothing else you can do works as well.
On arrival, go outside and walk somewhere in daylight. A tired person wants the hotel room with the curtains shut, and that extends the adjustment.
The moderate lever: meal timing
Eating on destination time is a real secondary signal, and it starts on the aircraft. Set your watch to destination time when you board. Treat the cabin service as optional: you can skip a meal that lands at 3am destination time and sleep instead.
Alcohol on a long flight buys shallow sleep and a worse arrival. Drink water as you normally would.
Arrival-day decisions
- Do not sleep for four hours in the afternoon. A nap of twenty to thirty minutes, early in the day, is survivable and sometimes necessary. A long afternoon sleep leaves you awake at 2am and pushes the adjustment back a day, often two.
- Stay up until a plausible local bedtime. Somewhere near normal is enough. It is much easier if you are outside and moving than if you sit down.
- Book nothing important for the first morning. If you have a meeting, a tour with a fixed start or a train you cannot miss, put a day between it and your arrival. The buffer costs one day of your trip. Without it you turn up unable to think.
- Eat a real meal at a local mealtime, even without appetite. It is a signal, and it prevents the 4am hunger that wakes you fully.
Our own routine
- Set your watch to destination time at boarding.
- Sleep on the plane if it is night where you are going. Stay awake if it is not.
- Land, drop your bags and go outside for a walk in daylight, however appealing the bed looks. This takes willpower for about ninety minutes.
- Eat a simple dinner at a local hour and go to bed at something like a normal time.
- Schedule nothing before mid-morning the next day.
Not medical advice
This is our own approach from doing the eastward trip a lot. Nothing here concerns supplements or medication. If you take anything on a schedule, ask a pharmacist or doctor about a large time shift before you fly, and do not improvise at altitude.