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.
Method & Sources
We model your body clock with published light phase-response curves: bright light after your core-body-temperature low (about two hours before your usual wake time) nudges your clock earlier, and light before it nudges you later. Realistic adjustment is about 1–1.5 hours per day — advances are slower than delays — so a big time change takes several days, and we show your two clocks converging rather than an instant fix. Light windows are estimates from your usual sleep times, not a personal prediction; everyone shifts at a different pace. Timezone differences come from your two cities' local clocks on the departure date.
Educational, Not Medical Advice
Daily Vitality tools organize information and published guidance — they don't diagnose conditions, and they're not a substitute for care. Talk with your doctor, pharmacist, or another clinician about what's right for you.
This tool makes no alertness, safety, or fitness-to-drive claims. Persistent sleep trouble, or shift work that never feels right? Shift-work sleep disorder is a real, treatable thing — worth a conversation with a clinician. And talk to one before starting any supplement, melatonin included.
Sources: human phase-response curves to light (e.g., Khalsa et al. 2003; St Hilaire et al. 2012 — citation strings pending clinician review); entrainment pace ~1–1.5 h/day and CBTmin ≈ 2 h before habitual wake per published circadian literature. Melatonin framing from consumer-health guidance, never a dose; in Canada melatonin is a licensed natural health product (NPN). City time zones: IANA timezone database via your browser. This tool stores nothing you enter — your inputs live only in this page's URL.