Jet Lag Calculator: Your Light and Bedtime Plan by Time Zone

How long does jet lag last?

As a rule of thumb, your body clock moves about one hour a day after an eastward flight and about an hour and a half a day after a westward one. Cross six zones flying east and most people need five or six days to feel fully adjusted; the same trip westward takes about four. Jet lag is usually noticeable from three zones upward, and flying east is harder because the clock has to move earlier, the direction it resists.

The planner above turns those rules into a schedule for your trip: how far the clock has to move, how much of that you can do before you leave, and when to seek or avoid bright light once you land.

How the planner works

• Zones crossed. The difference between the two time zones on your departure date, including daylight saving where it applies. A 13 hour difference is treated as an 11 hour shift the other way, because the clock takes the shorter route.
• Your temperature low. The body clock's reference point is the core temperature minimum, about two to three hours before your usual wake time. Bright light in the hours after it moves the clock earlier; bright light in the hours before it moves the clock later. Every window in the tables is built from your wake time and moves a little each day as the clock shifts.
• Preparing before the flight. Moving bedtime and wake time by an hour a day for up to three days, with light at the right time, takes a real chunk out of the adjustment. The table shows the schedule for each preparation day.
• The first three days. The destination table gives a target sleep window in local time plus the hours to seek and avoid bright light. Sunglasses count as avoiding light when you have to be outside.

Flying east and flying west

What about melatonin for jet lag?

A Cochrane review of ten trials found that melatonin taken close to the target bedtime at the destination reduced jet lag in nine of them, for flights crossing five or more time zones. Amounts from 0.5 mg to 5 mg worked similarly on most measures, although people fell asleep faster on 5 mg. Timing mattered more than amount: taken at the wrong time of day it can push the clock the wrong way. If you are considering it, this guide to choosing a low dose covers timing and the research, and the planner's sleep window tells you which local hour counts as bedtime.

Six things that make any plan work better

1. Set your watch to destination time when you board and eat on that schedule.
2. Caffeine in the destination morning only. The caffeine cut-off calculator gives you the last-cup time for the new bedtime.
3. Nap no longer than 30 minutes on the first day, and not after mid-afternoon local time.
4. Move your meals and exercise into the new daytime; both are secondary time cues.
5. Short trips of two days or less: consider staying on home time rather than adjusting twice.
6. Run your usual wind-down in the new time zone. Familiar sequence, new clock.

Sources

1. Eastman CI, Burgess HJ. How to travel the world without jet lag. Sleep Medicine Clinics. 2009;4(2):241-255.
2. Burgess HJ, Crowley SJ, Gazda CJ, Fogg LF, Eastman CI. Preflight adjustment to eastward travel: 3 days of advancing sleep with and without morning bright light. Journal of Biological Rhythms. 2003;18(4):318-328.
3. Khalsa SBS, Jewett ME, Cajochen C, Czeisler CA. A phase response curve to single bright light pulses in human subjects. Journal of Physiology. 2003;549(3):945-952.
4. Waterhouse J, Reilly T, Atkinson G, Edwards B. Jet lag: trends and coping strategies. The Lancet. 2007;369(9567):1117-1129.
5. Herxheimer A, Petrie KJ. Melatonin for the prevention and treatment of jet lag. Cochrane Database of Systematic Reviews. 2002;(2):CD001520.

These studies looked at light, sleep timing and melatonin as an ingredient in travellers and volunteers. None of them tested a Veluna product; this page relates to individual ingredients and habits and is not the Veluna product.