Jet Lag Planner
Estimate your jet lag adjustment time when crossing time zones.
How Jet Lag Works
Your body follows an internal clock, known as your circadian rhythm, that is tuned to the day and night cycle of the time zone you usually live in. When you travel across time zones, that internal clock stays set to your departure time zone for a while, even though the local time, daylight, and activities around you have changed. This mismatch between your internal clock and the local environment is what causes the tiredness, alertness problems, and disrupted sleep commonly known as jet lag.
Eastbound vs Westbound Travel
The direction you travel affects how your body needs to adjust. Eastbound travel moves you into a time zone that is ahead of your departure time zone, which generally means your body has to adjust to an earlier schedule, something most people find more difficult. Westbound travel moves you into a time zone that is behind your departure time zone, generally requiring your body to adjust to a later schedule, which tends to be easier for most travelers.
General Adaptation Tips
A few general strategies can help your body adjust more quickly after crossing time zones: try to get exposure to daylight at your destination during local daytime hours, avoid long naps that can delay adjustment, stay hydrated, and try to align your meal times with the local schedule as soon as possible. For longer time zone changes, gradually shifting your sleep schedule in the days before you travel can also help. These are general suggestions only and may not work the same way for everyone.
FAQ
What causes jet lag?
Jet lag happens when your internal body clock, which is tuned to the time zone you traveled from, is out of sync with the local time at your destination. The larger the time difference, the longer it generally takes your body clock to adjust.
Why is eastbound travel often harder than westbound travel?
Eastbound travel shifts your schedule earlier, asking your body to fall asleep and wake up sooner than it is used to, which most people find harder to do. Westbound travel shifts your schedule later, which tends to be easier because it is closer to staying up later than usual.
How is the estimated adjustment time calculated?
The calculator takes the absolute time difference between your departure and destination time zones, in hours, and treats each hour of difference as roughly one day of adjustment, rounded to the nearest whole day. This is a general guideline, not an exact prediction.
Is this medical advice?
No. This calculator provides general travel planning guidance only and is not medical advice. If you have health concerns related to travel, sleep, or jet lag, consult a qualified healthcare professional.
Does crossing fewer time zones mean no jet lag at all?
Crossing only one or two time zones typically causes little to no noticeable jet lag for most travelers, though factors such as overnight flights, sleep quality, and travel fatigue can still affect how you feel.