How long jet lag lasts
Jet lag ends when the body clock reaches local time. Left alone the clock moves about one hour per day eastward and 1.5 hours per day westward, which is what sets the recovery figures below.
The recovery rule
Recovery time is a function of two things: how many zones you crossed, and which way you went. The commonly cited figures are one day per zone eastward and about two thirds of a day per zone westward. Both describe a traveller who takes no deliberate action, follows local daylight as it happens to fall, and lets the clock drift into place.
| 3 zones east | About 3 days without a plan |
|---|---|
| 3 zones west | About 2 days without a plan |
| 6 zones east | About 6 days without a plan |
| 6 zones west | About 4 days without a plan |
| 8 zones east | About 8 days without a plan |
| 8 zones west | About 5 days without a plan |
| 11 zones east | About 11 days without a plan |
| 12 zones either way | About 8 days without a plan, taken as a delay |
The figures are averages. Age, chronotype, sleep debt carried onto the flight and the light a traveller happens to meet on arrival all move the number in either direction.
What shortens recovery
Three levers move the clock, and all three work through timing rather than quantity.
- Timed bright light. The strongest lever by a wide margin. Four hours of bright light on the correct side of your body clock low point moves the clock further in one day than anything else available.
- A fixed sleep window. Holding a set bedtime and wake time keeps each gained hour in place. Sleeping whenever tiredness arrives lets the clock drift back.
- Timed melatonin. A smaller push in the same direction, and only when the timing is right. The wrong hour moves the clock the wrong way.
Preparation days matter because they move part of the work to before departure. Three days of preparation on an eastward trip bank three hours at home, where the bedroom, the routine and the darkness are already familiar. Those three hours are three days removed from the recovery at the far end.
Recovery with a plan
A plan does not change how fast a body clock can move. It changes how much of the movement happens before you land, and it removes the days lost to light exposure that pushed the clock the wrong way.
The Jet Lag Calculator states both figures for your route: the days the shift takes with the plan, and the days it would take without one. The difference between them is what the schedule is worth.
Questions about jet lag recovery
How long does jet lag last?
Without intervention, jet lag clears at roughly one day per time zone crossed travelling east, and roughly two thirds of a day per zone travelling west. A six zone eastward trip therefore takes about six days, and the same trip westward takes about four.
Can you recover from jet lag faster?
Yes. Timed bright light is the strongest lever, a fixed sleep window holds each gained hour in place, and correctly timed melatonin adds a smaller push. Preparation days before departure bank part of the shift at home, which shortens the days spent recovering at the destination.
Why does westward recovery take less time?
The unentrained human body clock runs slightly longer than 24 hours, so it drifts later on its own. Westward travel asks for a later clock and moves with that drift at about 1.5 hours per day. Eastward travel asks for an earlier clock and moves against it at about one hour per day.
Does one night of good sleep fix jet lag?
No. One night of sleep clears travel fatigue, which comes from the journey itself. Jet lag is a clock position problem, and a clock only moves when light and sleep timing move it. Sleeping longer without changing timing does not shorten it.
Should I nap after landing?
A short nap of 20 to 30 minutes early in the local afternoon restores alertness without eroding sleep pressure for the coming night. A long nap late in the day removes the pressure that would otherwise carry you into local bedtime, which lengthens recovery.