acalculator

How long is my jet lag recovery?

Type how many hours ahead or behind your destination's clock is, and whether you fly east or west. The jet lag calculator estimates your recovery in days at the CDC's average rates, 1 hour a day after flying east and 1.5 hours a day after flying west, and the date your body clock should match the local time.

Your numbers

Direction
Days to adjust
6

Your jet lag recovery takes about 6 days after flying east across 6 hours of time difference.

Days to adjust, unrounded
6
Hours to shift after landing
6
Adjustment rate
1 hour a day (east)
Adjusted by
October 8, 2026
Answer
Your jet lag recovery takes about 6 days after flying east across 6 hours of time difference
Note
Expect jet lag: 2 or more time zones crossed.

Answer for the example date Friday, October 2, 2026. It changes to today's date when the page loads.

Days to adjust: 6. Your jet lag recovery takes about 6 days after flying east across 6 hours of time difference.

How to calculate

Estimates jet lag recovery days from the hours of time difference and the direction you fly, at the CDC’s average of 1 hour a day eastward and 1.5 hours a day westward, less any hours you shift before the trip.

Example with the default inputs (Time difference (hours) 6, Direction East (clock ahead), Days of shifting sleep before the trip 0, Arrival date October 2, 2026) on the example date Friday, October 2, 2026: Your jet lag recovery takes about 6 days after flying east across 6 hours of time difference.

Method: Days to adjust = (time difference − hours shifted before the trip) ÷ rate, rounded up; rate = 1 hour a day east, 1.5 west.

  • The CDC’s average rates: the body clock shifts 1 hour a day after flying east and 1.5 hours a day after flying west.
  • Each day of shifting sleep before the trip moves the body clock 1 hour toward the destination.
  • People vary; light, sleep and timing change how fast you adjust.

Machine-readable copies: Markdown, JSON.

Worked examples

Each example is checked against the calculator on every build.

  1. Time difference (hours) 6, Direction East (clock ahead), Days of shifting sleep before the trip 0 gives Days to adjust 6, Days to adjust, unrounded 6, Adjustment rate 1 hour a day (east), Answer Your jet lag recovery takes about 6 days after flying east across 6 hours of time difference.Source: Riedy and Williams, Jet Lag Disorder, CDC Yellow Book 2026 (average adaptation 1.5 hours a day westward and 1 hour a day eastward; jet lag follows travel across at least two time zones; shifting sleep 1 hour a day for 2 to 3 days before the trip reduces the time to adjust), https://www.cdc.gov/yellow-book/hcp/travel-air-sea/jet-lag-disorder.html (retrieved 2026-10-02)
  2. Time difference (hours) 6, Direction West (clock behind), Days of shifting sleep before the trip 0, Arrival date 2026-10-02 gives Days to adjust 4, Days to adjust, unrounded 4, Adjusted by 2026-10-06.Source: Riedy and Williams, Jet Lag Disorder, CDC Yellow Book 2026 (average adaptation 1.5 hours a day westward and 1 hour a day eastward; jet lag follows travel across at least two time zones; shifting sleep 1 hour a day for 2 to 3 days before the trip reduces the time to adjust), https://www.cdc.gov/yellow-book/hcp/travel-air-sea/jet-lag-disorder.html (retrieved 2026-10-02)
  3. Time difference (hours) 8, Direction West (clock behind), Days of shifting sleep before the trip 3 gives Days to adjust 4, Days to adjust, unrounded 3.333333, Hours to shift after landing 5.Source: Riedy and Williams, Jet Lag Disorder, CDC Yellow Book 2026 (average adaptation 1.5 hours a day westward and 1 hour a day eastward; jet lag follows travel across at least two time zones; shifting sleep 1 hour a day for 2 to 3 days before the trip reduces the time to adjust), https://www.cdc.gov/yellow-book/hcp/travel-air-sea/jet-lag-disorder.html (retrieved 2026-10-02)
  4. Time difference (hours) 1, Direction East (clock ahead), Days of shifting sleep before the trip 0 gives Days to adjust 1, Note Under 2 hours of difference: jet lag disorder is not expected..Source: Riedy and Williams, Jet Lag Disorder, CDC Yellow Book 2026 (average adaptation 1.5 hours a day westward and 1 hour a day eastward; jet lag follows travel across at least two time zones; shifting sleep 1 hour a day for 2 to 3 days before the trip reduces the time to adjust), https://www.cdc.gov/yellow-book/hcp/travel-air-sea/jet-lag-disorder.html (retrieved 2026-10-02)

How it works

For a time difference of H hours (0 to 12), flown east or west, with S days (0 to 3) of shifting sleep 1 hour a day before the trip:

  1. Hours to shift after landing L = H − S, or 0 when S is H or more.
  2. Rate r = 1 hour a day flying east, 1.5 hours a day flying west (the CDC's averages).
  3. Days to adjust, unrounded = L ÷ r.
  4. Days to adjust (the headline) = that number rounded up to a whole day.
  5. Adjusted by = the arrival date + the days to adjust, when you give the arrival date. A date after 9999-12-31 is left out.

Note. With H under 2 the page says jet lag disorder is not expected (the CDC's definition needs at least two time zones); otherwise it says to expect jet lag. The days are still shown.

Rules

  • H is from 0 to 12 hours and may have a fraction (5.5 for India from the UK in winter). S is a whole number from 0 to 3.
  • The arithmetic is exact: 5 ÷ 1.5 is 3⅓ days, which rounds up to 4.
  • "East" means the destination's clock is ahead of home; "west", behind.

Output format. The unrounded days have 2 decimals. The rate reads "1 hour a day (east)" or "1.5 hours a day (west)". The answer reads "Your jet lag recovery takes about 6 days after flying east across 6 hours of time difference" ("1 day" and "1 hour" when either is one).

Worked examples by hand

New York to Paris, 6 hours east. 6 ÷ 1 = 6 days.

Paris to New York, 6 hours west, landing 2 October 2026. 6 ÷ 1.5 = 4 days, adjusted by 6 October 2026.

8 hours west after 3 days of shifting. L = 8 − 3 = 5; 5 ÷ 1.5 = 3.33, rounded up to 4 days.

1 hour east. 1 ÷ 1 = 1 day, and under 2 hours jet lag disorder is not expected.

Other questions people ask

How long does jet lag recovery take?

On average the body clock shifts about 1 hour a day after flying east and 1.5 hours a day after flying west (CDC Yellow Book). A 6-hour trip east takes about 6 days; the same trip west takes about 4.

Why is flying east worse than flying west?

Flying east means going to bed earlier by your body's clock, which is harder than staying up later. The body's own daily rhythm runs a little longer than 24 hours, so most people find it easier to delay their clock than to advance it.

How many time zones cause jet lag?

The CDC describes jet lag disorder after travel across at least two time zones. With a 1-hour difference you may feel a little off for a day, but jet lag disorder is not expected.

Can I adjust before I leave?

Yes. The CDC says shifting your sleep 1 hour a day toward the destination time in the 2 to 3 days before the trip (earlier for east, later for west) can shorten the time to adjust. Each day you shift takes 1 hour off the difference here.

What helps me adjust faster after I land?

Light at the right time. Bright morning light helps the clock move earlier, which helps after flying east; evening light helps it move later, which helps after flying west. Keep to local meal and sleep times.

What if the time difference is more than 12 hours?

This page takes up to 12 hours. A clock 14 hours ahead is also 10 hours behind, so type the shorter difference and the direction that matches it.