Jet Lag Recovery
Planner

The body clock adjusts at roughly 1 hour per day when flying east (phase advance) and about 1.5 hours per day when flying west (phase delay), because the intrinsic circadian period is slightly longer than 24 hours. A 5-hour eastward trip therefore takes about 5 days to fully adapt, while an 8-hour westward trip takes about 6 days. The planner shows your specific countdown.

Your internal clock runs on about a 24.2-hour cycle, so delaying it (westward travel) is natural and easy, while advancing it (eastward travel) fights your biology. That's why eastward trips feel harder and take longer to shake off — roughly 1 hour of adaptation per day eastward versus 1.5 hours per day westward.

Yes — light is the strongest time cue (zeitgeber) for the circadian clock. Bright light in the biological morning advances the clock (helps after flying east); bright light in the biological evening delays it (helps after flying west). The planner times your seek-light and avoid-light windows based on your remaining jet lag each day.

Melatonin's phase-response curve is roughly opposite to light's: taking it in the evening (about 30 minutes before your target bedtime) advances the clock, which helps after flying east; taking it in the morning helps delay the clock, which helps after flying west. The planner recommends the right timing for your direction of travel.

Yes — pre-adaptation works. Shifting your sleep schedule by about 30 minutes per day toward the destination's time, starting 2-3 days before departure, roughly halves the jet lag you feel on arrival. The planner includes a pre-departure schedule as part of your plan.

No. Your cities, dates, and flight times are processed entirely in your browser. Timezone offsets are computed with the browser's built-in Intl API, and nothing is uploaded, stored, or tracked — there is no server and no account.