Estimated Jet Lag Recovery
After traveling East across 9 time zones
Estimated Full Recovery By
Saturday, March 7, 2026
Estimated Recovery Duration
9 days
This is just an estimate. Recovery can be affected by factors like age, health, and sleep habits.
Sample Flight Details
- Traveler: Jordan
- Departure: America/New York on November 1, 2024
- Arrival: Asia/Tokyo
How the Estimate is Built
- Compare time zones: The departure offset of -4 hours and arrival offset of 9 hours differ by 11 time zones after adjusting for the international date line.
- Determine travel direction: Because the arrival offset is larger, the trip moves eastward, making it a(n) east journey.
- Apply the recovery rule: Traveling east uses the 1 day per time zone rule, which results in 11 recovery days.
Adding those recovery days to the departure date suggests Jordan should feel adjusted by November 12, 2024.
The Rule of Thumb
This calculator uses a common and widely accepted rule of thumb for estimating jet lag recovery. The core idea is that your body's internal clock (circadian rhythm) can only adjust so much each day.
- Determine Time Zones Crossed: First, the calculator finds the difference in UTC offset between your departure and arrival time zones. For example, New York (UTC-4 in summer) to London (UTC+1) is a 5-hour difference.
- Determine Direction of Travel: It identifies whether you traveled East (advancing time) or West (reversing time).
- Apply Recovery Rate:
- Traveling East: The body finds it harder to advance its clock. The rule is approximately 1 day of recovery per time zone crossed.
- Traveling West: It's easier for the body to delay its clock. The rule is approximately 2/3 of a day of recovery per time zone crossed.
- Calculate End Date: The calculated number of recovery days is added to your departure date to estimate when you'll feel fully adjusted.
Example From Your Trip
- From: UTC
- To: Asia/Tokyo
- Direction: East
- Time Zones Crossed: 9
Because you are traveling east across 9 time zones, the calculator estimated it will take 9 days for your body to fully adjust. Adding this to your departure date gives an estimated full recovery by March 7, 2026.
How it works
The calculator estimates circadian recovery from UTC-offset difference and travel direction. It computes time zones crossed, then applies a direction factor: eastbound ≈ 1.0 day per zone, westbound ≈ 0.67 day per zone. The result is rounded and added to your travel date as an adjustment target.
Worked real-world examples
- New York to London (east, 5 zones): about 5 recovery days.
- Los Angeles to Tokyo (west, 8 zones by offset math): about 5–6 recovery days.
- Paris to Dubai (east, 3 zones): about 3 recovery days before normal alertness returns.
Common mistakes
- Counting flight hours instead of time-zone shift.
- Ignoring DST differences, which can change zone gap by 1 hour seasonally.
- Treating the result as exact despite sleep debt, caffeine, alcohol, and light exposure effects.
When not to use this tool
- For pilots, cabin crew, or shift workers on regulated fatigue-risk programs.
- For travelers with diagnosed circadian rhythm disorders requiring specialist treatment.
- When planning medication or melatonin protocols without clinician input.
Sources and standards
- Sleep medicine rule-of-thumb models for eastbound vs westbound circadian adaptation speed.
- AASM and CDC travel-health guidance on light timing, sleep hygiene, and fatigue management.
Frequently Asked Questions
Find answers to common questions about this calculator below.