Timeshifter is a dedicated jet lag app: tell it about your trip and your sleep, and it builds a personal, hour-by-hour plan for light, sleep, caffeine and more. Our free jet lag calculator answers the quick questions instantly, in the browser: how big the time difference is, which way your body clock has to move, roughly how many days it takes, and a simple plan. For a big trip where every day counts, Timeshifter's personal plan is worth a look. For everything else, the calculator is free and takes ten seconds.
Disclosure: Flight is our product, and this blog belongs to it. We've tried to be fair: what we say about Timeshifter comes from its own site and app listings, checked in October 2026. Apps change, so check prices there before you decide.
At a glance
| Flight | Timeshifter | |
|---|---|---|
| What it is | A free jet lag calculator, part of Flight's tools | A personalised jet lag planning app |
| Runs on | Any browser | iPhone and Android |
| Account or install | Neither | App install and a trip profile |
| Personal to your sleep | No: general rules of thumb | Yes: built from your sleep habits and trip |
| Plan detail | Time difference, direction, days to adjust, three-step plan | Hour-by-hour advice, with reminders |
| Related tools | Sunrise times, time zones, sleep and caffeine calculators | Built into the plan |
| Price | Free | First plan free; paid plans after |
Where Timeshifter is stronger
Personalisation. Timeshifter takes your usual sleep times, chronotype and itinerary, and tells you when to seek and avoid light, when to sleep, and when caffeine helps, hour by hour, with notifications so you don't have to open the app. It also recognises short trips, where staying on home time can be the better plan. For a long-haul trip that matters, like a big meeting the day after landing, that level of detail can be worth paying for.
Where our jet lag calculator is stronger
- Free and instant. Two airports, and the answer is on screen: no install, no account, no profile.
- The shape of the problem. It shows the time difference, the direction your clock has to move (taking the shorter way round), and how many days it's likely to take, which is what most trips need.
- The tools around it. Sunrise and sunset times for timing daylight, the time zone converter, the sleep calculator and the caffeine calculator, all free.
- The guides. Our day-by-day jet lag plan and light timing guide explain the why, not just the what.
A trip with each
With Timeshifter, you'd enter your flights, your usual sleep times and your chronotype a few days before a trip to Tokyo. It then tells you, hour by hour, when to seek light, when to wear sunglasses, when to sleep and when coffee helps, and reminds you through notifications.
With the jet lag calculator, you'd enter New York and Tokyo and see straight away that the body clock has to move, the shorter way round, and roughly how many days that takes, with a three-step plan. Then the sunrise tool tells you when daylight is in Tokyo, and the caffeine calculator when to stop coffee. All free, all in the browser.
Using both
- Check the calculator first: if the shift is small, you may not need a plan at all.
- For a big shift and an important trip, a personalised plan from Timeshifter adds detail.
- Either way, the basics are the same: light at the right time, local meal times, a fixed wake-up time.
Who should choose which
- Timeshifter for a high-stakes long-haul trip where you want a personal, hour-by-hour plan.
- The jet lag calculator for quick answers, planning ahead, and most everyday trips.
And before you go
Flight can fly your route at your desk as a focus session, as long as the real trip: a good way to clear your work before you leave.
