Jet Lag Adjustment Days
The body clock only moves an hour or so a day: roughly 1 hour when travelling east and 1.5 westward. The same number of time zones therefore costs different amounts depending on direction.
Your numbers
Days to adjust
8d
Hours
1h
Time zones crossed
8h
What it means
8 zones east takes about 8 days; going east shortens your day, which is harder.
Formula
Days to adjust = Time zones crossed ÷ (1.5 − 0.5 × Direction (E1 / W0))
Morning light speeds up eastward shifts and evening light speeds up westward ones. Moving meals and bedtime to local time on arrival helps most of all.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| Time zones crossed (h)The clock difference between departure and arrival. | 8 | 1 ~ 14 |
| Direction (E1 / W0)Direction of travel — enter 1 for east, 0 for west. | 1 | 0 ~ 1 |
Step by step
Quick reference table
Results when only Time zones crossed (h) changes and everything else stays put.
| Time zones crossed (h) | Days to adjust (d) | Hours (h) | Time zones crossed (h) |
|---|---|---|---|
| 4 | 4 | 1 | 4 |
| 6 | 6 | 1 | 6 |
| 8 | 8 | 1 | 8 |
| 12 | 12 | 1 | 12 |
| 14 | 14 | 1 | 14 |
What each result means
| Result | At default values |
|---|---|
| Days to adjust (d)Days until the body clock lines up with local time. | 8 |
| Hours (h)A duration counted in hours. | 1 |
| Time zones crossed (h)The clock difference between departure and arrival. | 8 |
Common mistakes
Morning light speeds up eastward shifts and evening light speeds up westward ones. Moving meals and bedtime to local time on arrival helps most of all.
Glossary
- Time zones crossed
- The clock difference between departure and arrival.
- Direction (E1 / W0)
- Direction of travel — enter 1 for east, 0 for west.
- Days to adjust
- Days until the body clock lines up with local time.
- Hours
- A duration counted in hours.
Frequently asked questions
Q. How is Jet Lag Adjustment Days calculated?
Days to adjust = Time zones crossed ÷ (1.5 − 0.5 × Direction (E1 / W0)) — The body clock only moves an hour or so a day: roughly 1 hour when travelling east and 1.5 westward. The same number of time zones therefore costs different amounts depending on direction.
Q. Can you walk through an example?
With Time zones crossed 8h, Direction (E1 / W0) 1, the answer is Days to adjust 8d.
Q. What do I need to enter?
Enter Time zones crossed, Direction (E1 / W0). The result recalculates as you type, and an empty box counts as zero.
Q. How much does the answer move if I change a number?
Changing only Time zones crossed (h) moves the answer to Time zones crossed (h) 4 → Days to adjust (d) 4 and Time zones crossed (h) 14 → Days to adjust (d) 14. The table below lays out five steps.
Q. How are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
Q. Anything to watch out for?
Morning light speeds up eastward shifts and evening light speeds up westward ones. Moving meals and bedtime to local time on arrival helps most of all.
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These calculators help you understand health figures; they do not replace diagnosis or prescription. See a clinician if you have symptoms.