Shift - Jet Lag Sleep

Most jet lag apps prescribe a plan on day zero and then forget about you. Shift is different. It uses your Apple Watch wrist temperature — the data your watch already collects every night — to estimate where your body clock actually is, and adapts the protocol every morning as your body responds. A sleep copilot for people who fly often • Plan a trip, get a day-by-day light, sleep, caffeine, and meal protocol before, during, and after the flight. • Each morning, Shift re-fits its model against last night's wrist temperature, heart rate, HRV, and sleep midpoint, and rewrites the next three days of cues. • See your current body time alongside local time, with an honest confidence interval — "estimated ± 42 min" beats a fake-precise readout. • A predicted alignment timeline shows when your body is expected to catch up. • Between trips, Everyday mode keeps your rhythm steady and shrinks the social jet lag that builds up at home. The science • Wrist temperature is a clinically supported proxy for core body temperature minimum (CBTmin) — a gold-standard circadian phase marker. • Light cues follow the published Phase Response Curve: morning bright light to advance eastward, evening light to delay westward. • Adaptation rate is learned per user with a Bayesian update after every trip. Eastward and westward speeds are tracked separately — most people adapt 30–50% slower eastward, and the protocol reflects that. For frequent flyers • Designed for people crossing 4+ time zones at least 6 times a year — international consultants, investment bankers, salespeople, expat executives, crew, touring musicians. • Works best with Apple Watch Series 8 or newer (the first model that records wrist temperature). Without one, Shift uses population estimates and wider confidence intervals. • iPhone 12 or newer for the on-device model. Privacy • Everything runs on your phone. No accounts. No servers. No analytics SDKs. • HealthKit data stays local. Shift only reads — never writes back to Health. • Trip data is yours to export as PDF for medical records, expense reimbursement, or your own files. Access • Starter access includes a single-trip protocol preview. • Trip Pass unlocks a 14-day full protocol, reminders, and cue logging for a single trip. • Shift+ adds unlimited trips, real-time phase tracking, Everyday mode between trips, your weekly report and adaptation profile, PDF export, the Watch app, and Family Sharing where available. • Terms of Use (EULA): https://www.apple.com/legal/internet-services/itunes/dev/stdeula/ • Privacy Policy: https://w3h9uf.github.io/shift/privacy.html Wellness, not medical. Shift does not diagnose or treat any condition and is not a substitute for medical advice.