Jet lag is the gap between the time on the wall and the time on your body. The bigger the gap, the longer your circadian system needs to catch up — and the harder it is to push through with willpower alone. This planner gives you a schedule for the three days before you fly, what to do on arrival, and the recovery window that follows.
Eastward travel is harder than westward, and the math reflects that. Your body's natural circadian period is about 24.2 hours, which means your internal clock drifts later on its own. Going west — phase-delaying — works with that drift. Going east — phase-advancing — works against it. The accepted recovery rate in the literature is roughly one day per time zone heading east, and about 0.7 day per time zone heading west.
The planner does three things. First, it shifts your bedtime by an hour each day for three days before the flight, in the direction of your destination. That closes part of the gap before you board. Second, it gives you an arrival-day plan focused on getting onto the local meal and sleep schedule. Third, it tells you when to seek bright light at destination — morning for eastward travel, late afternoon for westward — because light is the strongest zeitgeber, the cue your circadian system pays the most attention to.
Caveats. This is a planning tool, not medical advice. People with epilepsy, bipolar disorder, or on light-sensitive medications should ask their physician before using bright light therapy. Melatonin can help but is not in this tool — dosing depends on direction and timing in ways that benefit from individual guidance.
The planner lays out a schedule of when to seek light, when to avoid it, and when to take melatonin, built from your direction of travel and the number of zones crossed. Flying east it advances your clock, so it front-loads morning light and evening melatonin; flying west it delays your clock, so it leans on evening light instead.
The pre-flight rows matter as much as the arrival ones. Shifting your clock a little each day before an eastward trip means you land already part-adjusted, which is far easier than trying to snap your body to a new time zone overnight.
As Burgess and Eastman describe, bright light is the most powerful synchroniser of the human clock, and melatonin acts as a weaker dark-pulse signal in roughly the opposite direction. Their phase-response curves show that light in the morning and melatonin in the evening both advance the clock, while light in the evening delays it.
Timed together correctly, the two can shift your clock by around an hour to an hour and a half a day. Timed wrongly, light in particular can push you the wrong way and deepen the lag, which is exactly why a schedule beats guessing.
For eastward flights, start advancing your sleep and light exposure one to three days early. On arrival, get outdoor daylight at the local times the plan calls for and deliberately avoid it at the wrong ones, since sunglasses and shade are as much a tool here as sunlight.
Anchor everything else to destination time immediately: eat, sleep and socialise on the new clock even when your body protests. Keep naps short and strategic so they do not sabotage the first local night, and accept that the plan is only as good as your adherence to it.
Your body's free-running circadian period is about 24.2 hours — slightly longer than a day. That means without external cues, you would drift to a later sleep time each day. Westward travel asks your body to do exactly that — go to bed later. Eastward asks the opposite, which is why it takes more days and feels harder. The rule of thumb is one day per time zone east, about 0.7 day per time zone west.
It can help, but the dosing and timing are direction-specific and matter more than the dose itself. For eastward travel, low-dose melatonin (0.5mg) in the early evening at destination can help phase-advance. For westward, melatonin in the early morning at destination can help phase-delay. Get specific timing from a pharmacist or sleep clinician — generic advice does more harm than no advice.
Shifts of 1 to 2 hours usually adapt within a day or two with no formal preparation. The biggest lever is syncing to local meal and sleep times immediately on arrival. The planner gives you a soft recommendation in this band rather than a full pre-flight schedule.
You can in theory, but in practice 1 hour per day is what most people sustain alongside normal work and family obligations. The planner caps the pre-flight shift at 3 hours total over 3 days. If you have flexibility for longer prep — a week of vacation before a major trip — you can shift 30 minutes per day for up to 6 days for a smoother adjustment.
If your destination time matches local night, sleep. If it does not, stay awake. The deciding factor is what time it will be at destination when you land — try to arrive close to your local bedtime, not in the middle of a local afternoon. A short eye-mask + earplugs nap on a daytime-arrival flight is fine but stop sleeping 2-3 hours before you land.
Eastman & Burgess 2009 review in Sleep Medicine Clinics consolidated the evidence and the AASM 2007 clinical guideline (Sack et al.) endorses similar rates. Both papers are the standard references for circadian adjustment to travel — the rates are population averages and individual variation is wide, but they hold up across studies.
Find the destination bedtime that aligns with the new wake time.
Get the right dose + timing for jet-lag use specifically — different from sleep-onset use.
Track the post-flight recovery window.
On long flights east, caffeine timing makes or breaks the shift.
On arrival day, the right nap shape can salvage or wreck your reset.
The circadian-mismatch story behind the planner's recommendations.