Jet Lag Planner

Do Jet Lag Apps Work? An Honest Answer Before You Pay

You're standing at the departure gate, thumb hovering over the button, half-convinced you're about to pay ten dollars for a glorified countdown timer. It's a fair suspicion. The good ones work, just not in the way the app stores imply. None of them deletes jet lag, because nothing does. What a decent app actually does is take the handful of things that genuinely move your body clock, mostly daylight caught at the right hour and caffeine used with a bit of discipline, and turn them into a schedule you'll still follow at 2am in an unfamiliar hotel room. The shifting is your biology's job. The app supplies the timing and the nudge to stick with it, which sounds trivial right up until the night you'd have got both wrong on your own.

What's actually under the hood

Strip the branding off any credible jet lag app and you find the same short list of tools underneath. Light does most of the work, which is why it gets its own deep dive in Light: The Most Powerful Jet-Lag Lever. Step outside and you're standing in light anywhere from a couple of times brighter than a lit room, on a filthy overcast day, to a couple of hundred times brighter in open sun, and depending on whether you catch it before or after your body's daily low point, it drags your clock later or pulls it earlier. Caffeine, timed to your new morning, backs the light up. Melatonin has real trial evidence behind it too, though what you can legally buy differs at every border and whether you go near it is a conversation for you and your doctor, not for an app (there's more on that in Melatonin and Jet Lag: What the Science Says). The catch that ties all of them together is timing. Every one of these tools can shove your clock the wrong way if you use it at the wrong hour, and working out the right hours for a specific flight, on a specific day, given your own sleep habits, is fiddly enough that handing it to software earns its place.

Timeshifter

Timeshifter is the most detailed of the big names, and it's the one worth reaching for on a brutal itinerary. Its plans come out of published circadian science and cover light, caffeine, naps, and melatonin timing, tuned to your exact flights and to whether you're a morning lark or a night owl. It has picked up some real credibility along the way: the CDC Yellow Book, the travel-health reference doctors actually reach for, named it in its 2024 edition, though the current 2026 edition dropped named apps and now just describes "jet lag calculators" generically. The pricing is freemium: your first plan free, then $9.99 a plan or $24.99 for a year of unlimited ones. If you fly long-haul often and want melatonin timing built into the plan, it's the most complete paid option out there. For the one big holiday a year, though, think twice, since a free tool will hand you much the same core light schedule without the price tag.

Jet Lag Rooster

Jet Lag Rooster is the best-known free option, and it's been around since 2013. A researcher called Jay Olson built it, then at Simon Fraser University, and Sleepopolis hosts it these days. Feed it your flights and it returns an hour-by-hour light and melatonin schedule drawn from the same circadian logic the paid apps run on. The interface is plain and the output is a wall of text rather than anything you'd screenshot on the plane, but the advice is sound and it costs nothing, which counts for a lot. For a one-off trip where all you want is the hours, it does the job without any fuss.

The limits no app will mention

The app-store screenshots skip this part. Nothing erases jet lag, and no app can move your clock faster than your body will physically allow. Even with every hour timed perfectly, the clinical protocols put the ceiling at roughly 2 hours a day when you're delaying and 1.5 when you're advancing, against the 1.5 and 1 you'd drift at anyway. A real improvement, and nowhere near a reset button. Software can't make you follow the plan either, and a plan you ignore at the hotel bar does exactly nothing. The bigger trap is that these apps are only as clever as what you type into them: get your landing time wrong by an hour, or pick the wrong chronotype because you weren't sure, and the app will hand you a confident schedule pointing the wrong way with no idea anything is off. And, obviously, none of it is medical advice.

Fun fact

Every one of these apps is ultimately reading off the same graph, and that graph was built by keeping volunteers in windowless rooms for weeks. To work out which way light shifts a human clock, researchers had to shut people away from daylight entirely, hold the lighting flat and dim, then deliver a single measured pulse of bright light at a different hour for each participant and track what happened to their temperature and hormone rhythms afterwards. Plot all those results and you get a phase response curve, the chart that says light at this hour advances you and light at that hour delays you. Your travel app is a wrapper around it.

Where the Jet Lag Planner comes in

One more belongs on the list, with a note of self-interest attached: the planner on this very site. The Jet Lag Planner is the honest version of the category: free, no account, nothing stored on a server. It draws your trip as an animated world map turning through day and night, then lays out a day-by-day plan for light, caffeine, and sleep. Two deliberate choices set it apart. It leaves melatonin protocols out, partly because what you can legally buy differs at every border, from prescription-only in the UK to a shelf supplement in the US, and partly because a dose belongs to you and a clinician rather than to a web page. And it will tell you plainly when a trip is simply too small to be worth fighting, a two-hour hop or a couple of nights away, which turns out to be a whole topic in When Not to Fight Jet Lag: Short Trips and Small Shifts. If you'd rather understand the full method first, How to Beat Jet Lag: A Science-Based Guide is the place to begin; otherwise hand it a route and let it plan, like jetlagplanner.app/plan?from=LHR&to=HND.

Sources

General wellness information, not medical advice. Talk to a clinician before changing your schedule if you have a sleep or health condition.

Last reviewed August 5, 2026.

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Jet Lag Planner

A free tool that shows your flight across daylight and darkness, then builds an honest day-by-day light and sleep plan. No account, and your trip is worked out in your browser rather than on a server.

General wellness information, not medical advice. Talk to a clinician before changing your schedule if you have a sleep or health condition. © 2026 XOR Limited.