Jet Lag Calculator and Adaptation Guide

Belize, Costa Rica, El Salvador, Guatemala, Honduras, and Nicaragua run on UTC-6 (also written GMT-6), Central Standard Time. Panama is the exception at UTC-5. None of the seven countries uses daylight saving time, so their clocks stay the same all year, and the gap from your home changes by an hour when your own country moves its clocks.

The human body clock runs slightly longer than 24 hours, so it finds it easier to stay up later than to fall asleep earlier. That is why flying west is usually easier than flying east. The CDC Yellow Book gives average adaptation rates of about 1.5 hours per day westward and about 1 hour per day eastward, and the more time zones you cross, the harder it gets.

From the United States, Mexico, the Caribbean, or South America, the difference is at most three hours, so jet lag is mild or absent. From Europe it is 6 to 8 hours, which at the CDC average rate is roughly four to five days to adjust fully when flying west. From Asia or Australia the shift is 8 to 10 hours the shorter way around, and at about an hour per day full adjustment can take eight to ten days. These are averages, and people differ.

Before you fly, the tool suggests moving your bedtime in steps of 30 to 45 minutes over the two to five days beforehand. On the plane, it suggests setting your watch to destination time, following the day and night of your destination, avoiding alcohol, drinking water, and moving every hour or two. After you land, it covers light, meals, exercise, and sleep on local time.

Light is the strongest signal for your body clock, and it switches off the melatonin that helps you sleep. The tool gives suggested windows for your route: outdoor light soon after waking when your clock needs to move earlier, and afternoon light, around 3 to 7 pm local time, with dark sunglasses or indoor time in the morning when it needs to move later. For very large time differences the best window can be counterintuitive, so treat the tool’s times as a starting point.

Eat on local time from your first day and drink plenty of water. The tool suggests protein at breakfast, heavier carbohydrates such as beans or bananas in the evening, and hydration that includes local options like coconut water. The evidence for food timing is thin, since a BMJ Clinical Evidence review found no studies testing eating patterns for jet lag, so treat these steps as support rather than a cure.

The tool builds in rest windows: a short nap of 20 to 30 minutes before mid-afternoon if you need one, staying up until about 10 pm local time on your first night, and relaxation techniques such as 4-7-8 breathing and a body scan to help you wind down. These are general suggestions and the tool does not adjust for age, so families traveling with young children should ask a pediatrician about naps and bedtimes.