Jet Lag Calculator
Adapt to a new time zone in half the time with a tailored plan.
Jet lag is not just tiredness - it is your internal clock running on old time while the world runs on new time. Your circadian rhythm naturally shifts about one hour per day, which is why crossing six time zones can mean nearly a week of grogginess if you let nature handle it alone. This calculator builds a day-by-day adaptation plan based on your departure and arrival time zones, the direction of travel (eastward is harder than westward), and your arrival time. It combines the three interventions research has identified as most effective: controlled light exposure, strategic caffeine timing, and shifted sleep schedules. The output is a simple daily checklist: when to seek sunlight, when to avoid it, when to nap if needed, when to go to bed. Follow it for 2-3 days before departure and through your first few days on arrival, and you will typically halve your adaptation time.
The Science
Circadian adaptation research consistently shows three high-impact levers: timed light exposure, scheduled sleep shifts, and caffeine timing. Research by Czeisler at Harvard demonstrated that properly timed bright light can shift the circadian clock by 3+ hours per day - far faster than the natural 1-hour drift. Eastward travel is harder because advancing the clock (going to bed earlier) is biologically more difficult than delaying it. Our calculator accounts for these asymmetries.
How It Works
Enter your departure and arrival time zones.
Enter your arrival time at destination.
The calculator figures direction and magnitude of the shift.
It builds a pre-trip and post-arrival schedule.
Follow the light and sleep cues each day.