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Jet Lag Calculator
Compare two time zones, see the exact time difference, and get a personalized plan to beat jet lag.
How this works
We use your device's live clock and the official IANA time-zone database (via the browser Intl API) to compute the exact offset between the two places you pick, including daylight saving time. The jet lag estimate follows the general rule of about one hour of adjustment per day and is for guidance only.
Disclaimer: This tool is for general informational purposes only and is not medical advice. If you have chronic sleep problems, please consult a healthcare professional.
References
- Waterhouse, J., Reilly, T., Atkinson, G., & Edwards, B. (2007). Jet lag: trends and coping strategies. The Lancet, 369(9567), 1117–1125.
- IANA tz database (2026 release).
- Centers for Disease Control and Prevention. (2023). Jet Lag. cdc.gov.
Frequently asked questions
How long does jet lag last?
Roughly 1 day per time zone crossed for westward travel, 1-1.5 days for eastward. Most people take 4-7 days to fully adjust to a 6+ hour time zone change. The direction matters because your body clock adjusts by ~1-2 hours per day, and advancing (east) is harder than delaying (west).
How do I prevent jet lag when flying east?
Shift your sleep schedule 1-2 hours earlier for 3-5 days before departure. On the plane, set your watch to destination time immediately and sleep on the schedule. Bright light in the destination morning helps you advance your clock. Melatonin 0.5 mg 5 hours before destination bedtime also helps.
Does melatonin help with jet lag?
Yes, modestly. Take 0.3-0.5 mg at the destination's bedtime, starting the day you arrive. For eastward travel, taking it 5 hours before target bedtime for 3-5 days before departure can pre-shift your clock. Avoid doses above 1 mg — they're no more effective.
Should I nap when I arrive after a long flight?
A short nap (under 30 min) before 3 p.m. destination time is fine and helps you push through until bedtime. A long nap (over 1 hour) or late-afternoon nap will make it harder to sleep at night. The goal: stay awake until local bedtime, then sleep a full night.
Why is eastward jet lag worse than westward?
Eastward travel requires your body clock to advance (sleep earlier), which is harder than delaying (sleep later). Your body has a natural tendency to lengthen the day, so going to bed earlier is fighting your biology. This is why crossing 6+ time zones eastward can take a week to fully adjust.