The Body Clock Shifter
Beat jet lag — and night-shift lag — with light. Tell us your trip or your new schedule: watch your body clock catch up with the local one, day by day, and see exactly when to seek and avoid bright light.
~1–1.5 h/day
how fast a body clock actually shifts — advances are slower
Timed light
bright light around your body's early-morning low moves the clock
Jet lag & night shift
same mechanism, same plan — travel or a new schedule
Jet lag isn't random — it's a measurable gap between your internal clock and the local one. Published research maps how bright light moves that internal clock: light just after your body's early-morning temperature low shifts you earlier; light just before it shifts you later. Time the light right and the gap closes in days. Time it wrong and you push the clock the wrong way — which is why the plan tells you when to avoid light, too.
The same mechanism covers a schedule change — days to nights, or an early shift that starts before dawn. Enter your current and new sleep windows and the plan treats it exactly like a flight across time zones: the clocks converge at a realistic pace, with light sought and avoided at the right hours. It's a large, underserved audience the paid jet-lag apps barely mention.
This tool is educational, not medical advice — no alertness, safety, or fitness-to-drive claims, and light windows are population-level estimates. Nothing you enter is stored — inputs live only in this page's URL.