Why is eastward travel harder than westward?

Traveling east forces your body to advance its internal clock, which is harder because the human circadian rhythm naturally runs slightly longer than 24 hours. Going west extends your day, which is more in line with your natural tendency. Recovery east takes roughly 1 day per time zone crossed; west takes about 0.67 days per zone.

What is the light exposure recommendation based on?

Light is the primary cue that resets the circadian clock. When traveling east, morning light at your destination accelerates the phase advance needed. When traveling west, evening light delays your clock to match the new time zone.

How accurate is the recovery estimate?

The estimate uses the widely cited rule of thumb: 1 day per time zone crossed eastward, 0.67 days per zone westward. Individual recovery varies based on age, fitness, sleep quality, and caffeine or melatonin use.

Does this tool send my data anywhere?

No. All calculations run entirely in your browser. Nothing is transmitted to any server.

What if my origin and destination are in the same time zone?

If the UTC offsets at your travel date are identical, there is no jet lag. The tool will report zero hours difference and no adjustment needed.

Jet Lag Calculator

Name: Jet Lag Calculator
Availability: InStock
Author: Nham Vu

Enter your origin and destination time zones, travel date, and normal sleep schedule to get a jet lag severity estimate, recovery timeline, and a 7-day adjustment plan.

Trip Details

Origin Time Zone

Destination Time Zone

Travel Date

Normal Sleep Schedule (at origin)

Bedtime

Wake Time

Enter your trip details on the left, then click Calculate.

Expected Recovery

7-Day Adjustment Plan

Day	Bedtime	Wake Time	Notes

Recovery estimates use the standard 1 day/zone east, 0.67 days/zone west rule of thumb. Individual results vary.

Done!

Summary

Enter your origin and destination time zones, travel date, and normal sleep schedule to get a jet lag severity estimate, recovery timeline, and a 7-day adjustment plan.

How it works

Select your origin time zone from the dropdown.
Select your destination time zone.
Enter your travel date.
Enter your normal bedtime and wake-up time.
Click "Calculate" to see your jet lag severity, expected recovery, and a 7-day sleep adjustment plan.

Use cases

Plan sleep adjustments before a long-haul international flight.
Estimate how many days to allow for recovery before an important meeting.
Understand whether eastward or westward travel will affect your body more.
Follow a day-by-day schedule to minimize jet lag on vacation or a business trip.

Frequently Asked Questions

Last updated: 2026-06-10 · Reviewed by Nham Vu