Jet Lag Calculator

Pick your home time zone and your destination to see how many hours you are crossing, which direction is harder on your body clock, and roughly how long it will take to adjust.

Why Jet Lag Is Worse Traveling East

Most people find it easier to stay up later than to fall asleep earlier, which is why traveling east — which requires going to bed and waking up earlier than usual — tends to produce more jet lag than traveling the same number of zones west. Flying from North America to Vietnam is a good example: heading west across the Pacific is a large time change, but because it is westward, the body clock generally adapts a bit faster than the same number of zones in the eastward direction.

Before You Fly

Shifting bedtime by 30-60 minutes per night in the direction of your destination for a few days before departure gives your body a head start. Getting morning sunlight if you are shifting earlier, or evening light if shifting later, reinforces the new schedule faster than sleep timing alone, per standard sleep-science guidance on light exposure and circadian rhythm.

After You Land in Vietnam

Once you land, try to get outside in daylight as soon as possible and hold off on a full nap until closer to local bedtime — a short 20-30 minute rest is fine, but a long daytime sleep will slow the adjustment. Staying hydrated and going easy on alcohol for the first day or two also tends to make the adjustment noticeably smoother.