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Jet Lag Planner

The method for turning a route, a direction of travel, and a length of stay into a light and sleep schedule for the days around a time-zone change.

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The tool

Plan the days around the flight

Give the planner your route, your dates and the sleep window you keep at home. It reads the time-zone database already sitting in your browser, works out which way your clock has to move and how far, and lays out the light and the sleep for the days either side of the flight.

This applies general light and timing principles to your route. It cannot measure how fast your own clock shifts, which differs between people and between directions of travel, so read the plan as a reasonable default to adapt rather than a schedule to obey. Do not follow a light-timing instruction here that conflicts with what your own clinician told you.

The form below runs in your browser, so it needs JavaScript to work. The published method further down this page does not need one, and it is the part worth reading first.

The route

Both lists come from the time-zone database in your browser, so they know every offset and every clock change without asking a server. Nothing about your itinerary leaves this device.

The flight

Departure is on the clock where you take off. Arrival is on the clock where you land.

This changes the whole strategy. Under two nights the CDC advice is not to adapt at all, and the planner will say so.

The sleep you keep at home

Both ends, on your home clock. This is the window the plan moves.

What you can control

Light is the planner’s main lever. How much of it you have a say over changes what the plan is worth.

Nought to three. The CDC describes moving sleep an hour a day over the two or three days before you fly.

How much say you have over the light around you

Where what you type goes

Nowhere. Everything above runs in this browser, on this device. Restadian never receives what you enter, because nothing here sends it anywhere.

What this tool will not tell you, and why

  • How many days a traveller needs before a plan has worked. The CDC gives an average rate of adaptation, about an hour a day east and an hour and a half west, and calls it an average. Dividing your time difference by it produces a number of days that looks like a forecast. The planner shows the pace and the direction and stops there, because the arithmetic is not the uncertainty.Riedy & Williams, Jet Lag Disorder, CDC Yellow Book
  • How far before bed to bring the light down. Evening light delays the clock, and ordinary room lighting is enough to do it, and the study that showed this ran across the whole eight hours before bed. Nobody has turned that into a number of minutes you should dim for. The planner opens the evening window where your own sleep opportunity opens, which is a boundary the duration recommendation already gives it, and does not dress the width up as a finding.Gooley et al., Exposure to room light before bedtime suppresses melatonin onset and shortens melatonin duration in humans · Watson et al., Recommended Amount of Sleep for a Healthy Adult

Every number above, and where it came from

Each figure this tool uses is registered in the code with the sentence it was taken from. Open one and you can check the number against the source without taking our word for it.

  1. Riedy & Williams, Jet Lag Disorder, CDC Yellow BookCenters for Disease Control and Prevention · 2026
    The sentence the figure came from
    an average rate of adaptation of 1.5 hrs/day for westward travel and 1 hr/day for eastward travel … Exposure to bright light in the morning following the circadian nadir (approximately 2–4 hours prior to habitual wake time) promotes phase advances … exposure in the evening generally promotes phase delays … For short trips (e.g. less than 2 days), avoid adapting … Shifting sleep 1 hour later (for westward travel) or earlier (for eastward travel) per day in the 2–3 days prior to the trip may reduce the amount of time required to adjust … Short daytime naps (20–30 minutes) can be utilized to help sustain alertness during the local day, while longer daytime naps may interfere with subsequent nighttime sleep.
  2. Eastman & Burgess, How to travel the world without jet lagSleep Medicine Clinics · 2009
    The sentence the figure came from
    bright light can help produce phase advances when applied late in the sleep episode and in the morning after the Tmin, and can help produce phase delays when applied early in the sleep episode before the Tmin … Bright light is avoided after waking … because it could coincide with the phase advance portion of the light PRC … When the circadian clock phase shifts in the opposite direction to the shift in the LD cycle and sleep/wake schedule, this is considered re-entrainment in the “wrong” direction (antidromic re-entrainment) … phase advance the circadian clock for crossing up to 7 time zones east and phase delay the clock for crossing 8 or more time zone east.
  3. Sack et al., Circadian rhythm sleep disorders: part I — AASM reviewSleep · 2007
    The sentence the figure came from
    Exposure to the morning light after an eastward flight of more than eight time zones could retard adaptation to local time because it would be “hitting” the wrong area of the light PRC. Likewise, late evening light following a westward flight could retard adaptation for the same reason … The circadian system is most sensitive to light during the biological night, when humans normally sleep, and is least sensitive to light about midday.
  4. Khalsa et al., A phase response curve to single bright light pulses in human subjectsThe Journal of Physiology · 2003
    The sentence the figure came from
    A relatively rapid transition from phase delays to phase advances occurs near circadian phase 0 h [the core body temperature minimum] … peak-to-trough amplitude of 5.02 h … phase delays up to −3.60 h and phase advances up to +2.01 h.
  5. Czeisler et al., Stability, precision, and near-24-hour period of the human circadian pacemakerScience · 1999
    The sentence the figure came from
    the intrinsic period of the human circadian pacemaker averages 24.18 hours in both age groups, with a tight distribution consistent with other species.
  6. Watson et al., Recommended Amount of Sleep for a Healthy AdultAmerican Academy of Sleep Medicine & Sleep Research Society · 2015
    The sentence the figure came from
    Adults should sleep 7 or more hours per night on a regular basis to promote optimal health. Sleeping more than 9 hours per night on a regular basis may be appropriate for young adults, individuals recovering from sleep debt, and individuals with illnesses.
  7. Drake et al., Caffeine effects on sleep taken 0, 3, or 6 hours before going to bedJournal of Clinical Sleep Medicine · 2013
    The sentence the figure came from
    The magnitude of reduction in total sleep time suggests that caffeine taken 6 hours before bedtime has important disruptive effects on sleep and provides empirical support for sleep hygiene recommendations to refrain from substantial caffeine use for a minimum of 6 hours prior to bedtime.
The method

What it measures, what it assumes, and where that breaks down

What it estimates

How far your internal clock needs to move, in which direction, and a plausible pace for moving it, then a day-by-day arrangement of light and sleep timing that works with that direction rather than against it.

The time-zone database is already in your browser. The planner reads it there, which is why it knows about the clock change that falls inside your trip and why nothing about your itinerary has to leave the device to be told something the device already knew.

What it asks you for

  • Where you are flying from and to.
  • Your departure and arrival times.
  • Your usual sleep window at home.
  • How long you are staying.

That last one matters more than people expect. A two-day trip and a two-week trip call for different strategies, and for a short enough stay the sensible plan may be not to adjust at all, which the planner will say when it applies.

What it gives back

A schedule covering the days before you fly and the days after you land: when to seek light, when to avoid it, when to aim for sleep, and how far the plan expects to have moved by each day.

Eastward and westward travel are handled as the different problems they are. Moving your clock later is easier for most people than moving it earlier, and a plan that ignores direction is not much of a plan. Past about seven zones east the planner stops trying to advance your clock at all and delays it the long way round instead, because that is what the clock tends to do on its own at that distance.

The assumptions it rests on

  1. Direction of travel changes the difficulty. Advancing your clock and delaying it are not symmetrical tasks, and the plan is built around that asymmetry.
  2. Light timing is the primary lever available to a traveller. It is the one intervention that is free, available everywhere, and supported by a well-described mechanism.
  3. Partial adjustment is often the right goal. For short trips, fully shifting and then shifting back costs more than it returns.
  4. Your home sleep window approximates your starting phase. As with the Circadian Planner, this is a planning assumption rather than a measurement.

Where the numbers come from, and where they stop

The pace is the CDC’s: about an hour a day travelling east, an hour and a half travelling west. The pre-flight step is the CDC’s too, one hour a day over the two or three days before departure. The hinge the light advice turns on is the circadian nadir, roughly two to four hours before your habitual waking, and light after it pushes your clock earlier while light before it pushes it later.

Both light windows are closed by boundaries that already have a source: the middle of your waking day, where the AASM review says your clock is least sensitive to light, and the opening of your sleep opportunity, which is the AASM and SRS duration figure. Nobody publishes how long to stand in the light, so the planner marks where the window is and says nothing about how long.

One figure is missing on purpose. The CDC calls its rate an average, and dividing your time difference by an average produces a number of days that looks like a forecast. The planner shows the pace and the direction and stops there, because the arithmetic was never the uncertain part.

What it does not do

  • It does not recommend melatonin or any other supplement, and it does not calculate a dose or a timing for one. There is no automated dosing of anything, at any point, for any route, and no field in the plan one could live in.
  • It does not recommend prescription sleep medication or advise on using one you already take.
  • It does not advise on alcohol or caffeine as travel sleep aids.
  • It does not assess your fitness to work or to drive on arrival.

Limitations

It cannot know your individual rate of adjustment. People differ, and the same person can differ between trips.

It cannot see conditions at your destination: whether your mornings there will contain light, whether your schedule lets you be outside at the hour the plan asks for, or whether a seven o’clock meeting makes the whole thing moot. Telling it how much say you have over the light is the closest it gets, and where the answer is “almost none” it says plainly that its main lever has gone.