How to Use the Jet Lag Adjustment Estimator
Coming back from international travel often leaves you tired and foggy for days as your body struggles to catch up with a new time zone — commonly known as jet lag. This calculator takes the time zone difference between your origin and destination, plus the direction of travel (east or west), and estimates how many days it will take your body clock to adjust.
Your internal body clock naturally runs slightly longer than 24 hours, so westward travel — which lengthens your day — typically takes about 1 day per hour of time difference to adjust to, while eastward travel — which shortens your day — takes closer to 1.5 days per hour. That means the same 8-hour time difference will feel harder to adjust to when traveling east than when traveling west.
Since the Earth runs on a 24-hour cycle, the time difference you enter should always fall between 0 and 12 hours; a gap that looks larger is shorter when measured in the opposite direction. The result is only a rough estimate based on general rules of thumb — actual adjustment speed varies quite a bit with age, sleep habits, and how much daylight exposure you get after arrival.
Frequently Asked Questions
Your body's internal clock naturally runs slightly longer than 24 hours, so westward travel — which lengthens your day — is easier to adjust to, while eastward travel — which shortens your day and forces your rhythm to shift earlier — is harder and takes longer to adapt to.
Gradually shifting your bedtime and wake time toward your destination's schedule before you leave, getting plenty of daylight exposure after arrival, and cutting back on caffeine and naps can all help your body clock reset faster.
Since the Earth runs on a 24-hour cycle, the true time difference is always between 0 and 12 hours. A gap that looks like 13 hours is actually an 11-hour gap in the opposite direction, so enter the shorter direction and value.