Jet Lag Calculator
Get a personalized day-by-day recovery plan. Science-based light exposure, sleep timing and melatonin schedule.
Why jet lag happens
Your internal clock (circadian rhythm) is misaligned with local time. It affects sleep, hunger, alertness — and takes time to reset.
Bright morning light is the most powerful circadian signal. Getting sunlight at the right time can shift your clock by 1–2 hours per day.
Eastward travel requires advancing your clock (sleeping earlier). Westward means delaying it — which aligns with the human clock's natural tendency to run slightly long.
0.5–1mg melatonin taken at 9–10 PM destination time reduces jet lag severity by ~50%. Dose matters less than timing.
Alcohol fragments sleep architecture and worsens circadian disruption. Skip it for the first 2 days at your destination.
Common questions
Jet lag plan by direction and time zones
Travelers often search “how long does jet lag last,” “eastbound vs westbound jet lag,” and “when to take melatonin for jet lag.” The important inputs are direction, number of time zones, light exposure, and destination bedtime.
Flying east usually feels harder because you need to fall asleep earlier. Morning light at the destination helps advance your clock.
Flying west often requires staying awake later. Evening light can help delay your body clock and reduce early-morning waking.
Low-dose melatonin is most useful when timed to destination night, not taken randomly on the plane. Timing matters more than dose.
Sometimes the best move is avoiding light. Sunglasses, dim rooms, and screen reduction can prevent your clock from shifting the wrong way.