Calculator
Jet Lag Calculator
Eastward travel takes roughly one day per timezone to adjust. Westward travel takes about 1.5 days per timezone — because westward is essentially “extending” your day, which your body handles better. Light timing is the most powerful tool you have.
What it is at destination when you land.
Estimated adjustment
~6 days
Adjustment is roughly 1 day per timezone eastward. Eastward travel is harder because it shortens your day relative to your biological clock.
Light exposure plan
- Day 1: Bright light within 30 minutes of waking at destination. Avoid bright light in the evening.
- Day 2: Repeat morning light. Wake 30 minutes earlier than day 1 if possible.
- Day 3: Continue. Aim to be outside in the first hour after sunrise.
Melatonin guidance
0.3–0.5 mg at destination bedtime, starting the night you arrive. For 3–5 nights, then stop.
On arrival, eat meals at local times even if you're not hungry — meal timing is a secondary zeitgeber that supports circadian shift.
How it works
Jet lag is a temporary misalignment between your internal clock and local time. The clock isresettable, but slowly — roughly 1 hour per day under ideal conditions. That's why crossing six timezones takes the best part of a week to fully resolve.
Light is the strongest zeitgeber. Bright light in the morning at destination advances your clock (helps after eastward travel). Bright light in the evening delays it (helps westward). Get this wrong — exposing yourself to bright light at the wrong end of the day — and you can extend jet lag rather than shorten it.
Melatonin can help, mostly eastward, in low doses (0.3–0.5 mg) at destination bedtime. It's a timing signal, not a sedative — see melatonin timing.
Why it matters
People consistently exacerbate jet lag with poorly-timed light exposure (e.g. lying down in a dark hotel room mid-day after eastward travel — that's the worst possible move). A simple 3-day light schedule cuts adjustment time substantially.
Sources
- 1Eastman, C. I. & Burgess, H. J.. How to travel the world without jet lag · Sleep Medicine Clinics · 2009PMID 20204161