How long does jet lag last?
Updated 2026-08-17
About a day per time zone, if you do nothing. Eight zones, eight days. But that number is an average of two very different journeys — westward is roughly half again as fast as eastward — and it assumes you leave your body to work it out alone. Most of the wait is avoidable.
Why your body needs days at all
Your internal clock isn’t set by the clock on the wall. It runs on its own, and in the absence of any cues it settles into a day slightly longer than 24 hours. That small bias is why staying up late is easy and going to bed early is a fight.
Flying moves the wall clock instantly. Your body clock moves at its own pace — an hour or so a day — and until it catches up, everything that runs on it is in the wrong place: alertness, appetite, digestion, core temperature. That’s the part people describe as feeling “wrong” rather than simply tired.
The real numbers
| Direction | Typical pace | 8 zones takes |
|---|---|---|
| West (days get longer) | ~1.5 h/day | about 5 days |
| East (days get shorter) | ~1 h/day | about 8 days |
Night owls shift later even faster and earlier even slower; early birds are the reverse. It’s the single biggest source of variation between two people on the same flight.
What actually shortens it
Start before you leave. Three nights of shifting an hour at a time means landing three days ahead. This is the whole reason to plan a trip rather than react to it.
Get light at the right hour. Light is the strongest signal your clock has, and its effect reverses depending on when it lands relative to CBTmin. Right hour, you gain a day. Wrong hour, you lose one — which is worse than doing nothing.
Don’t sleep through the destination’s daytime. The nap that feels irresistible at 3pm on arrival day is borrowed from that night.
Consider going the long way round. For a big eastward jump it can be faster to delay 14 hours than to advance 10. See flying east vs west.
What doesn’t shorten it much
Hydration, exercise timing, special diets and fasting protocols all get attention. They are not useless, but they are second-order next to light timing and a sleep schedule you actually move. Fix those two first.