Your day-by-day recovery plan
| Day | Focus | What to do |
|---|---|---|
| 1 | Morning light exposure | Get bright light within 1 hour of local sunrise. Avoid bright light after 6 PM. Optional low-dose melatonin near local bedtime only if a clinician agrees. |
| 2 | Normalizing | Keep a fixed wake time. Morning light, daytime activity, consistent local bedtime. |
Why Jet Lag Happens — and How to Fix It
Jet lag is a mismatch between two clocks: the local time at your destination and your circadian rhythm, the roughly 24-hour internal timer that governs when you feel sleepy, hungry, and alert.1 That rhythm is set deep in the brain by the suprachiasmatic nucleus,1 and it does not care that your flight took twelve hours — it keeps running on home time until something forces it to shift.
The strongest signal that shifts the clock is light. Bright light in your biological morning pushes your rhythm earlier; light in the evening pushes it later.2 That is why the direction of travel changes the strategy: after an eastward flight the usual starting rule is destination-morning light and early nights, while after a westward flight it is afternoon light and staying up until local bedtime. The signal that actually moves the clock is light at your biological morning or evening, which may not match local clock time on a large shift. Melatonin can support the shift when timed with advice from a clinician.6
Direction matters because of a quirk of human biology: the natural circadian period is slightly longer than 24 hours,3 so delaying your clock (westward travel) is easier than advancing it (eastward).4 That is why the calculator above gives eastward trips a longer recovery estimate, and why the day-by-day plan for each direction prescribes opposite light strategies.
Recovery Time by Time Difference
Westward days follow the common “about one day per hour of time difference” rule. Eastward days use about 1.5 days per hour, because advancing the clock is harder.45 Individual recovery varies with light, sleep, and age.
| Time Difference | Westward Recovery | Eastward Recovery |
|---|---|---|
| 1–3 hours | 1–3 days | 2–5 days |
| 4–6 hours | 4–6 days | 6–9 days |
| 7–9 hours | 7–9 days | 10–14 days |
| 10–12 hours | 10–12 days | 15–18 days |
Frequently Asked Questions
How to recover from jet lag fast?
Anchor yourself to the destination schedule immediately: eat, sleep, and get light exposure at local times from day one. Morning light helps after eastward flights, afternoon light after westward ones. Keep naps under 20 minutes, stay hydrated, and avoid alcohol on arrival day.
How long does jet lag last?
A common rule of thumb is about one day of recovery per hour of time difference when flying west, and up to 1.5 days per hour when flying east. A 6-hour eastward trip can take 7–9 days to fully clear, while the same gap westward usually resolves in about 6.
Does melatonin help jet lag?
Low-dose melatonin is used for jet lag, especially after eastward flights. The useful part is when you take it relative to your body clock, not a high milligram number. Many travelers take 0.5–1 mg near destination bedtime; phase-shifting protocols sometimes take it earlier. This is not medical advice — ask a clinician if you take other medications or have a health condition.
Which direction is worse for jet lag?
Eastward travel is usually worse. Flying east shortens your day, forcing your body clock to advance — and most people's internal rhythm naturally runs slightly longer than 24 hours, so delaying (westward) comes more easily than advancing (eastward).
Sources
Numbers in the text point here. These are peer-reviewed papers, consensus statements, or official public-health pages you can open and check. The calculators still use planning averages; they are not a personal sleep study.
- National Heart, Lung, and Blood Institute. How Sleep Works: Your Sleep/Wake Cycle.
- Khalsa SBS, Jewett ME, Cajochen C, Czeisler CA. A phase response curve to single bright light pulses in human subjects. The Journal of Physiology. 2003;549(Pt 3):945–952.
- Czeisler CA, et al. Stability, precision, and near-24-hour period of the human circadian pacemaker. Science. 1999;284(5423):2177–2181.
- Waterhouse J, Reilly T, Atkinson G, Edwards B. Jet lag: trends and coping strategies. The Lancet. 2007;369(9567):1117–1129.
- CDC Yellow Book. Jet Lag. Travelers’ Health.
- Herxheimer A, Petrie KJ. Melatonin for the prevention and treatment of jet lag. Cochrane Database of Systematic Reviews. 2002;(2):CD001520.