Plan jet lag recovery across zones.
Jet lag is the gap between your internal clock and local time, and it closes at a rate of roughly one hour a day flying east or one and a half flying west. The asymmetry is real physiology: the free-running human circadian period is slightly longer than 24 hours, so delaying the clock (westward) matches its natural drift while advancing it (eastward) fights that drift. Recovery slows modestly with age as circadian amplitude declines. The behavioural advice matters as much as the arithmetic — a daytime arrival is an opportunity to anchor to local time immediately, and a long nap on arrival is the single most effective way to prolong the whole process.
Adjustment rate
Hours per day = base rate x age factor
Recovery time
Days = time zones crossed / adjustment rate
General wellbeing guidance, not medical advice. Circadian responses vary considerably between individuals, and jet lag can interact with medication timing, particularly for diabetes, epilepsy and hormonal treatments. Consult a doctor or pharmacist about medication schedules across time zones, and before using melatonin or any sleep aid.
Because the human body clock naturally runs slightly longer than 24 hours, so it drifts later if left alone. Flying west asks it to do exactly that. Flying east asks it to run short, which it resists — hence the roughly 50 percent slower recovery rate for the same number of zones.
Only briefly, and only early. A 20 to 30 minute nap before mid-afternoon relieves acute sleepiness without touching your sleep pressure for the night. A two-hour nap at 17:00 makes falling asleep at local bedtime nearly impossible and resets the whole adjustment by a day.