Jet Lag Recovery Calculator

The rule of thumb

Recovery days = zones × 1.0 eastward, or zones × 0.6 westward

7 × 1 = 7.0 days east; 7 × 0.6 = 4.2 days west.

Worked examples

7 zones east → 7.0 days
7 zones west → 4.2 days
3 zones east → 3.0 days
10 zones west → 6.0 days
5 zones east → 5.0 days

Why east is harder

Your body clock runs slightly longer than 24 hours, so delaying it — which is what westward travel asks — is the direction it drifts naturally. Eastward travel requires advancing the clock, against that tendency. The practical consequence is that a red-eye to Europe hurts more than the equivalent flight to California, even though the hours in the air are similar.

What actually speeds recovery

• Light at the destination morning. Bright morning light is the strongest signal for advancing the clock after eastward travel.
• Shift sleep before you fly. Moving bedtime an hour earlier for a few nights before departure reduces the deficit before it starts.
• Keep local meal times. Eating on the destination schedule reinforces the same signal.
• Avoid late caffeine and alcohol. Both fragment sleep, which is the mechanism the body uses to reset.
• Short naps, not long ones. A 20-minute nap restores alertness without resetting the night's sleep.

The estimate assumes a healthy adult on a normal schedule. Shift workers, children and anyone already sleep-deprived often need longer, and older travellers typically adjust more slowly.

Eastward travel is harder because the body clock runs slightly longer than 24 hours, so advancing it fights the natural drift while delaying it goes with it. The rule of roughly one day per time zone crossed puts seven zones at about a week, which matches the default. Light is the lever: morning light after an eastward flight pulls the clock earlier, evening light after a westward one pushes it later, and melatonin only helps when timed with that direction.

Frequently Asked Questions