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Guide

The International Date Line, and how a flight arrives before it leaves

Fly from Tokyo to Los Angeles and you land earlier on the same calendar day than you took off. Nothing unusual happened to the aircraft; you crossed a line in the Pacific where the date changes. This guide explains where the line runs, why it bends, and what it means for anyone booking across it.

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Where the line actually runs

The International Date Line sits roughly along the 180th meridian, opposite Greenwich. Cross it heading west and you skip a day; cross it heading east and you repeat one. It is not a treaty line — it exists because time zones have to wrap around somewhere.

It is also not straight. It bends east around Russia's Chukotka region, west around the Aleutians, and sharply east around Kiribati, which moved the line in 1995 so its entire territory shared one date. That bend created the current extreme: Kiribati's Line Islands run at UTC+14, while Baker Island sits at UTC−12. Those two points are 26 hours apart, meaning that for two hours each day, three different calendar dates exist somewhere on Earth.

For travellers the effect is straightforward but disorienting. A flight leaving Tokyo at 5pm on Monday and taking nine hours arrives in Los Angeles at around 11am on Monday — six hours before it departed, by the clock. Going the other way, a flight leaving Los Angeles on Monday evening arrives in Tokyo late on Tuesday, having apparently lost a day.

The practical advice is to trust the itinerary rather than the arithmetic. Airlines publish arrival times in local time at the destination, already adjusted. It is the connection times and the hotel bookings that catch people out, because a one-night stay can land on a date that never existed for the traveller.

Key facts

It follows the 180th meridian

Roughly, but with deliberate bends around inhabited territory.

Kiribati moved it in 1995

So the whole country would share a single date.

The extremes are 26 hours apart

UTC+14 in the Line Islands, UTC−12 at Baker Island.

Three dates can coexist

For two hours each day, three calendar dates exist somewhere.

Westbound loses a day

Eastbound repeats one.

Airlines already adjust

Published arrival times are local at the destination.

How to get it right

1

Read the itinerary dates

Check the arrival date, not just the time.

2

Count nights, not days

For hotels, book by the number of nights you will actually sleep.

3

Check visa dates carefully

An entry date can differ from the departure date by two days.

4

Use a converter for calls

Working out a call time across the line by mental arithmetic rarely ends well.

Questions people ask

By the clock, yes. Tokyo to Los Angeles departs late afternoon and lands the same morning, because the destination is on the other side of the date line.

Keep reading

Daylight saving explained

Which countries change their clocks, when they do it, and why the same two cities can be five hours apart one week and six the next.

UTC, GMT and Zulu time

What UTC actually is, how it differs from GMT, why aviation says Zulu, and when the distinction matters.

Scheduling across time zones

A practical method for booking meetings across zones: finding the overlap, rotating the pain, and stopping recurring calls from drifting.

Convert across the Pacific

City pairs that cross the date line show the day shift explicitly.

Open the converters