Jet lag calculator
Your body clock can shift about an hour a day going east and a bit more going west. This plan uses light and sleep timing to move it in the right direction.
Expected adjustment after arrival
4days
- 2 days beforeBed 10:00 PM, wake 6:00 AM (home time).
Seek: Bright light soon after waking
Avoid: Bright light in the last 2–3 h before bed - 1 day beforeBed 9:00 PM, wake 5:00 AM (home time).
Seek: Bright light soon after waking
Avoid: Bright light in the last 2–3 h before bed - Day 1 at destinationSleep 11:00 PM–7:00 AM local.
Seek: Light after 9:00 AM (morning of body time)
Avoid: Light for 3 h before 9:00 AM - Day 2 at destinationSleep 11:00 PM–7:00 AM local.
Seek: Light after 8:00 AM (morning of body time)
Avoid: Light for 3 h before 8:00 AM - Day 3 at destinationSleep 11:00 PM–7:00 AM local.
Seek: Light after 7:00 AM (morning of body time)
Avoid: Light for 3 h before 7:00 AM - Day 4 at destinationSleep 11:00 PM–7:00 AM local.
Seek: Light after 6:00 AM (morning of body time)
Avoid: Light for 3 h before 6:00 AM
Why east is harder than west
Your body clock has a pivot point a couple of hours before your usual wake time, near the low point of your core body temperature. Light after that point moves the clock earlier; light before it moves the clock later. After a long flight that pivot is sitting at a strange local hour, which is why the plan names specific times. Getting it backwards (like a sunny morning walk after flying east across eight zones) can push your clock the wrong way.
The clock also runs slightly longer than 24 hours in most people, so delaying (west) comes more easily. Studies of travellers put natural re-entrainment at roughly 1 hour per day eastward and 1.5 hours per day westward.
Same distance, different recovery
Approximate days for the body clock to catch up without deliberate light timing, using ~1 h/day east and ~1.5 h/day west (Waterhouse et al., 2007). Good light timing can shorten both.
More jet lag tactics
- Pre-shift at home by an hour a day if you can; Eastman and Burgess showed a 3-day advance with morning light reduces eastward jet lag.
- Caffeine in the local morning helps alertness; avoid it within 8 hours of local bedtime.
- Naps on arrival day: 20 to 30 minutes, not in the late afternoon.
- Short trips (two days or less): consider staying on home time.
Frequent flyers with ongoing sleep loss should also check the sleep debt calculator after the trip.
Questions people ask
How long does jet lag last?
A common rule of thumb is about one day per time zone crossed, but direction matters. The body clock naturally shifts later more easily than earlier, so westward trips often resolve at around 1.5 time zones per day and eastward at about 1 per day, sometimes slower.
Why is flying east worse?
Flying east means you must fall asleep and wake earlier than your body clock wants. Most people’s internal day runs slightly longer than 24 hours, so moving later (west) is easier than moving earlier (east).
How do I get over jet lag fast?
Time your light exposure: seek light at the times that push your clock in the right direction and avoid it at the wrong times. Shift your sleep by an hour a day for a few days before you leave, stay hydrated, keep caffeine early, and nap briefly if you must.
Should I sleep on the plane?
Sleep on the plane if it falls during the destination’s night. Otherwise, stay awake or take only short naps so you arrive with enough sleep pressure to sleep at local bedtime.
Does melatonin help jet lag?
A Cochrane review (Herxheimer and Petrie, 2002) found melatonin taken close to the target bedtime at the destination reduced jet lag for flights crossing five or more time zones. Check with a pharmacist or doctor first, as rules and suitability vary.
Is it worth adjusting for a short trip?
For trips of two days or less, many experts suggest staying on home time as much as possible rather than adjusting and then re-adjusting.
Sources
- Eastman CI, Burgess HJ (2009). How to travel the world without jet lag. Sleep Medicine Clinics, 4(2).
- Waterhouse J et al. (2007). Jet lag: trends and coping strategies. The Lancet, 369(9567).
- Herxheimer A, Petrie KJ (2002). Melatonin for the prevention and treatment of jet lag. Cochrane Database of Systematic Reviews.
- Khalsa SBS et al. (2003). A phase response curve to single bright light pulses in human subjects. Journal of Physiology, 549(3).