How Long Does Jet Lag Last?

Jet lag happens when you cross time zones faster than your internal body clock can adjust — and that clock only shifts about one hour per day on its own. Cross eight time zones and you're looking at roughly a week to fully sync, though the direction of travel changes everything. This calculator estimates your recovery time based on zones crossed, direction, and age, then gives you a concrete light-and-sleep plan to speed the adjustment.

Why Direction Matters So Much

Eastward travel is harder than westward, and there's a clear reason. Flying east (say, US to Europe) forces you to fall asleep earlier than your body wants — and your natural body clock actually runs slightly longer than 24 hours, making it easier to stay up late than to sleep early. Flying west means staying up later, which your clock tolerates comfortably. This is why the same eight-zone trip can take a week going east but only four or five days going west.

How to Use This Calculator

Enter the number of time zones you're crossing (the hour difference between departure and destination), your direction of travel, and optionally your age group, since adjustment slows somewhat with age. You'll get an estimated recovery time, the severity level, how much your clock shifts per day, when to start prepping, and — most usefully — whether to seek morning or evening light at your destination, which is the single most powerful tool for resetting your body clock.

Worked Example

Flying from New York to Paris crosses 6 time zones eastward. Estimated recovery is about 6 days (6 zones × 1 day). The plan: start shifting your bedtime earlier 3 days before you fly, seek morning light in Paris to pull your clock earlier, avoid bright screens late in the evening, and consider melatonin before your target bedtime. The same 6-zone trip in reverse (Paris to New York, westward) would take closer to 4 days and call for evening light instead.

Proven Ways to Beat Jet Lag

• Shift your schedule before you fly: move bedtime earlier (eastward) or later (westward) by an hour a day for a few days pre-trip
• Use light strategically: morning light for eastward travel, evening light for westward — light is the strongest signal to your body clock
• Adopt destination time immediately: set your watch on the plane and eat and sleep on the new schedule from arrival
• Stay hydrated, limit alcohol and caffeine around the flight — both disrupt sleep quality when you can least afford it
• Get sunlight and stay awake until a normal local bedtime on arrival, even if you're tired — napping too long resets the clock the wrong way

Plan the Rest of Your Trip

Check your allowed days in Europe with the Schengen 90/180 calculator, count down to departure with the days until calculator, and convert times across your destinations with the time zone converter. Budgeting the trip? The travel budget tools help you plan the spend.

Frequently Asked Questions