Jet Zzz — Free Jet Lag Planner

Jet Zzz is a free, browser-based jet lag planner. I built it because generic advice like "just sleep on the plane" never fit my real trips. Enter your flights, your usual sleep times and the commitments you cannot move, and Jet Zzz builds a day-by-day schedule for sleep, light exposure and caffeine that gradually shifts your body clock toward your destination.

Why jet lag happens

Your body runs on a circadian clock of roughly 24 hours, located in the suprachiasmatic nucleus of the brain. It controls when you feel sleepy, when your body temperature drops, when you are hungry and when you are most alert. The clock is reset each day mainly by light reaching your eyes. When you cross several time zones quickly, the local day and night no longer match your internal clock. The result is jet lag: poor sleep at night, heavy fatigue in the afternoon, low concentration, and often digestive trouble.

The clock can only move about one to one and a half hours per day on its own. That is why a seven-hour shift can leave you foggy for close to a week. Eastbound trips are usually harder, because they ask you to fall asleep earlier than your body wants, while the natural human rhythm tends to drift slightly later.

How Jet Zzz plans your adjustment

The planner uses the same tools sleep researchers describe: well-timed bright light, avoiding light at the wrong moment, a gradual shift of bedtime in the days before departure, and sensible caffeine timing. Instead of an ideal lab schedule, it respects real life: work hours, meetings, layovers and the number of days you actually have to prepare.

Four steps to your plan

  • Enter your flights — add every leg with departure and arrival cities and times, including layovers.
  • Set your adjustment preferences — choose a gentle, balanced or fast-track pace, your preparation window, and whether you use light or caffeine.
  • Add fixed activities — meetings or events that cannot move, so the schedule never fights them.
  • Generate and export — get a day-by-day plan and save it as a PDF or add it to your calendar.

Features

  • Multi-leg trips with layovers and red-eye flights
  • Personalized sleep, light and caffeine timing
  • Adaptation chart and world map of your route
  • Conflict check against fixed commitments
  • PDF and calendar (.ics) export
  • Available in English, Chinese, Japanese, French, German, Spanish and Italian

Frequently asked questions

Is Jet Zzz free?

Yes. It runs in your browser, needs no account and stores no personal travel data on a server.

How long does jet lag last?

Roughly one day per time zone crossed without a plan. A structured plan that starts a few days before departure can shorten this noticeably.

Is this medical advice?

No. Jet Zzz is an informational planning tool. Talk to a doctor before using melatonin or other sleep aids. See the safety notes.

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