Jet Laggard

What actually moves the needle, in plain terms. Nothing here is medical advice.

Light is the main lever — far more than caffeine, melatonin, or anything else on this list. Bright light in the hours after your body's lowest point pushes your clock earlier; light in the hours before it pushes later. That's why this app's windows move by a few hours each day rather than staying fixed.

Ordinary daylight — even on a cloudy day — is bright enough. You don't need a special lamp or device for most of this; a walk outside covers it.

After dark, keep the room lights on. It counts for less than daylight, and a bright lamp does more.

Sunglasses are not a substitute for avoiding light — measured against this app's own model, ordinary shades in direct sun still let through as much light as your eyes can use. Getting genuinely indoors, or into shade, is what an "avoid light" window actually means.

Source: CDC Yellow Book (light timing relative to your body clock's low point); Mayo Clinic (morning light flying east, evening light flying west).

Water. Drink plenty. Being dehydrated can make the symptoms of jet lag worse.

Move. Stretch and walk the cabin regularly.

Alcohol. Go easy. It breaks up your sleep and dries you out, which can make jet lag worse. In a lab study with cabin-level air pressure (about 8,000 ft), a moderate amount of alcohol pushed blood oxygen below the healthy range for hours during sleep and cut deep sleep.

Source: NHS (drink plenty of water; stretch and walk the cabin; too much caffeine or alcohol can make jet lag worse); CDC Yellow Book (stay hydrated; avoid excess alcohol, which fragments sleep and dehydrates); Trammer et al., Thorax 2024 (40 healthy adults, blood alcohol about 0.04%, simulated 2,438 m cabin).

Caffeine is a timing tool, not a fix. It helps you stay alert during the day you're trying to adjust to — but taken too late, it costs you the night's sleep, which sets you back further than it helped.

A reasonable rule flying west: stop caffeine at least 6 hours before the bedtime you're aiming for at your destination.

Source: CDC Yellow Book (westward travel caffeine protocol); Mayo Clinic (too much caffeine makes jet lag worse).

Exercise combined with light exposure may speed up how fast your clock adjusts. On the flight itself, getting up and walking the cabin periodically helps too, separately from any effect on your body clock.

Don't try to sleep through your destination's daytime to "catch up" — it delays the adjustment rather than helping it. Sleep at your destination's night, even if that means a rough first day.

Source: Mayo Clinic (light plus activity may speed adaptation); NHS (stay awake during destination daytime; stretch and walk on the flight).

This app is run by one person (the owner) for a small, invited group of family and friends, in the UK. This page says what's held about you and why, in place of a policy nobody could otherwise find.

Your email address and name, from however you sign in. Your trips and travel plans, your settings, sleep times you log, the phase data derived from them, whether you're following your plan, and — for the owner's account only — data pulled from an Oura ring. If notifications are on, your device's push subscription is stored so reminders can reach it. The app also records the date and time you last used it — a single value, overwritten each time and never kept as a history, so the owner can see which invited accounts were never opened. It can lag up to 15 minutes behind, and no pages or actions are tracked. It also keeps one yes-or-no answer: whether one category of advice is offered where you last used the app. That is decided from the country your connection appears to be in each time you open the app; the country itself is not stored.

To calculate and show your jet lag schedule — the thing this app exists to do. You joined by invitation and chose to enter this data. The things recorded automatically are when you last used the app and that yes-or-no answer, both described above; everything else is here because you put it in.

The legal basis is your consent. Sleep and body-clock data can reveal something about your health, so for that it is your explicit consent. You can withdraw it at any time by deleting the data or your account.

Nobody, by default. The app and its sign-in system are self-hosted by the owner — there is no third-party analytics or advertising. The exceptions, each seeing only what its job needs: Google, if you choose to sign in with Google (it tells the app your email address and name); Resend, which delivers sign-in emails (it sees your email address); the owner's email provider, which sends invitations; Cloudflare, which hosts jetlaggard.com — if you asked for an invitation there, it holds the email address, country and note you typed; a Web Push service, to deliver reminders if you turn them on (it sees only that a notification was sent, not its contents); and the Oura API, for the owner's own account only.

Your data stays until you remove yourself or are removed. After that it's kept for up to 7 days — your own undo window, not the owner's — then permanently deleted by a daily cleanup job. Asking for immediate, formal erasure skips that window entirely. Erasure also clears any invitation request you made through jetlaggard.com from the app; the original copy of that request stays with Cloudflare until the owner removes it, so ask if you want it gone.

You can see everything held about you, and delete your account and everything in it, from Settings → Your account. Both take effect immediately. For anything else — a question, a correction, an objection — contact the owner directly.