Jet lag calculator

The calculator reduces your two UTC offsets to the effective shift — the shorter path around the clock. Los Angeles to Tokyo is +17 raw hours, but the body experiences a 7-hour westward delay, which is exactly why that direction feels easier than the 7-hour eastward advance home. Recovery days then follow the asymmetry: zones × 1 day eastward, zones × ⅔ day westward, rounded up. Half-hour zones (India, Nepal, the Chathams) are handled — your clock doesn't round them off, so neither does the tool. For the light-based mechanics underneath, see the circadian rhythm calculator.

For crossings of four-plus zones, shifting your schedule 30–60 minutes a day toward the destination for the final 3–4 nights front-loads real adjustment: each shifted night is partial entrainment you don't have to do on arrival. The table above gives you the exact bedtimes and wake times, capped at a 3-hour total shift so the plan stays liveable — and the sleep schedule calculator turns the new anchor into a full week once you land. Flying tomorrow? Skip it — the light strategy below does the work.

Light is a phase shifter, and the direction of the shift depends on when it lands relative to your clock's nadir. Eastward, you owe your clock an advance: bright morning light pays it, evening light cancels the payment. Westward, the signs flip. The common mistake — a bright morning run after landing in Europe from the US, timed at the wrong phase — can push adjustment the wrong way for a day. Follow the seek/avoid pair the calculator prints for your direction.