Jet lag calculator

Why light timing matters more than anything else

Light is the strongest signal for resetting your body clock — but the same sunlight helps or hurts depending on your internal time. Light after your body’s low point (about 2 hours before you naturally wake) moves the clock earlier, which suits eastward travel; light before it moves the clock later, which suits westward travel. Get it backwards and jet lag gets worse, not better. That directional trap is what this calculator is built to avoid.

Short trips

For trips of 3 days or fewer across 3+ zones, the evidence says don’t adapt at all — stay on home time. Shifting twice is worse than not shifting. The calculator says so explicitly instead of giving you a fake adaptation plan.

Popular routes

Try a one-click plan (dates roll to next weekend automatically): New York → London, Los Angeles → Tokyo, Dubai → Sydney. Then read the London guide, Tokyo guide or Sydney guide.