Date-aware time-zone planning

Jet Lag Calculator

See how far the local clock changes, then build a realistic plan for before travel, the flight, and your first days after arrival.

1. Tell us the tripChoose cities, date, direction, and usual sleep times.

2. See the clock changeOffsets are checked for your selected travel date.

3. Choose practical stepsUse a conservative plan, not a strict medical schedule.

Time: About 1 minute
You enter: Six simple trip and sleep details
You receive: A planning guide, not a diagnosis
Privacy: Trip answers stay in this browser

Build your travel plan

All fields are required unless the cities have no local clock difference.

Origin city *

The calculator uses this city's time zone.

Destination city *

The calculator checks this city's date-aware offset.

Departure date *

Daylight-saving changes are checked for this date.

Which direction are you physically traveling? *

Direction matters around the international date line, so the calculator does not guess it from UTC offsets.

Your usual home schedule

These times are used only to make an optional pre-travel example.

Usual bedtime at home *

Use your ordinary home clock time.

Usual wake time at home *

The tool shifts bedtime and wake time together.

What jet lag means in everyday language

After fast travel across time zones, the local clock can change before your body clock catches up. You may feel sleepy, wide awake, hungry, or less focused at inconvenient local times. Travel sleep loss can add to these feelings, so not every tired day after a flight is caused by the clock shift alone.

Why the east or west choice matters

The same two city clocks can be connected by an eastward or westward route, especially near the date line. The tool asks instead of guessing.

🌅 Eastward travel

Your body clock generally needs to move earlier. A population-average planning rule is about one hour of adjustment per day, but a real trip can be faster or slower.

🌇 Westward travel

Your body clock generally needs to move later. A population-average planning rule is about 1.5 hours per day, but this is not a promise about how you will feel.

Common questions before a trip

How long will jet lag last?

The result shows a rough body-clock adjustment estimate, not a recovery deadline. Number of time zones, sleep loss, light, flight timing, health, and individual response all matter.

Should I sleep on the plane?

Use destination local time as a guide when it is practical: sleep if it is destination nighttime and you can do so safely. This tool does not know your flight or arrival time, so it cannot choose an exact in-flight sleep window.

How should I use daylight?

Ordinary daylight during the destination's local day can help provide local time cues. Exact bright-light exposure and avoidance can shift the body clock in different directions depending on timing, so this tool does not prescribe a personalized light window.

What about caffeine?

If you use it, keep caffeine to destination daytime and stop at least six hours before planned sleep. Sensitivity, serving size, medicines, pregnancy, and health conditions can change its effect.

Does the calculator tell me when or how much melatonin to take?

No. Incorrect timing can worsen misalignment, and products, medicines, pregnancy, age, and health context matter. Discuss melatonin with a clinician or pharmacist rather than using this plan as a dose or timing instruction.