As a rough guide, jet lag lasts about one day for each time zone you cross, so a six-hour shift takes roughly six days to fully clear. Recovery is usually faster after westward travel and slower after eastward travel, and it varies from person to person. Well-timed light exposure and a consistent local schedule can meaningfully shorten it.
Rough recovery guide
| Time zones crossed | Westward (delay clock) | Eastward (advance clock) |
|---|---|---|
| 3 zones | ~2-3 days | ~3 days |
| 6 zones | ~4-5 days | ~6 days |
| 9 zones | ~6-7 days | ~8-9 days |
| 12 zones | ~7-8 days | Adjusts via the shorter direction; can split |
Approximate, for orientation only. Individual recovery varies widely with age, chronotype, sleep before travel, and how well you time light. The clock shifts on the order of an hour a day, faster west than east.
What is the “one day per time zone” rule?
The most widely quoted rule of thumb is that it takes about one day to recover for each time zone crossed. Cross three zones and expect roughly three days; cross eight and expect over a week. The reason is simple: your body clock resets only gradually, shifting on the order of an hour a day, so the more hours you need to move it, the more days it takes. This rule is a useful starting estimate, not a precise law – it is an average that real people scatter around.
Why does westward jet lag clear faster than eastward?
Because the human clock naturally runs slightly longer than 24 hours, it is easier to stretch the day later (delay) than to pull it earlier (advance). Flying west asks for a delay, which the body does more readily, so recovery is often quicker – many people manage closer to 1.5 time zones per day westward. Flying east asks for an advance, which is harder, so eastward recovery is typically slower, often nearer one zone per day or less. This direction asymmetry is one of the best-established facts about jet lag; the timing science behind it is the phase response curve.
What makes some people recover faster than others?
Several factors move the estimate up or down:
- Direction of travel – west is usually faster than east, as above.
- Number of time zones – the dominant factor; more zones, more days.
- Light timing – getting bright light at the right local times, and avoiding it at the wrong times, is the strongest way to speed recovery. Getting it wrong can slow you down.
- Chronotype – your natural early or late tendency gives a modest edge in one direction.
- Sleep before travel and age – arriving rested helps; adjustment can take longer as people get older.
- Behaviour at the destination – keeping local mealtimes, activity and a fixed wake time reinforces the shift.
How can I make jet lag last a shorter time?
You cannot make your clock jump, but you can push it in the right direction faster. The core moves are: time your light exposure to the direction of travel (seek morning light and avoid late-evening light going east; seek evening light and avoid early-morning light going west); keep to the destination’s schedule for sleep, meals and activity from arrival; and, where appropriate and cleared with a clinician, consider timed melatonin. Starting the shift on the plane by sleeping toward the destination’s night also helps.
Because the ideal light windows depend on your exact route and move a little each day, a calculated plan is far more reliable than guesswork. Get a personalised estimate from the jet lag duration calculator, a full day-by-day plan from the jet lag calculator, and precise seek/avoid-light times from the light planner and adjustment planner.
Frequently asked questions
How long does jet lag last after a long-haul flight like Frankfurt to Tokyo?
Frankfurt-Tokyo is a large eastward shift of seven to eight zones, so full recovery commonly takes about a week, sometimes more. Good light timing and a consistent local schedule can shorten it. Use the jet lag calculator for a route-specific estimate.
Is jet lag worse coming back home?
Not inherently – what matters is the direction. The return trip is the opposite direction, so if the outbound leg was the harder eastward one, the return is the easier westward one, or vice versa.
Can jet lag last for weeks?
For most people it resolves within days to about a week. If jet-lag-like symptoms persist well beyond the expected adjustment for your trip, other causes may be involved – consider seeing a doctor.
Does staying up until local bedtime cure jet lag instantly?
It helps you align to local time, but it does not instantly reset your body clock, which still shifts gradually. Combine a local schedule with correct light timing for the fastest realistic recovery.
Sources
- U.S. Centers for Disease Control and Prevention – CDC Yellow Book, “Jet Lag” chapter – the approximate one-day-per-time-zone guide and the eastward/westward asymmetry.
- NHS – “Jet lag” (nhs.uk/conditions/jet-lag/), last reviewed 31 May 2023 – jet lag usually improves within a few days as the body adjusts.
- Eastman CI & Burgess HJ (2009). “How to travel the world without jet lag.” Sleep Medicine Clinics, 4(2) – adjustment rates on the order of an hour per day and how to accelerate them.
- Sleep Foundation – “Jet Lag” educational overview.
The recovery table applies the well-established ~1 h/day adjustment rate and the direction asymmetry from the sources above; it is an orientation estimate, not a clinical prediction. jetlag.info’s calculators implement the same principles as a transparent, non-medical heuristic.