How Time Zones Work

On 25 October 2026 clocks across Europe went back one hour as summer time ended. This film explains the system behind it: why noon moves fifteen degrees of longitude every hour, how every town once kept its own time, how railways brought London time to Britain and four zones to the United States in 1883, how the 1884 International Meridian Conference chose Greenwich, how GMT gave way to UTC, why China keeps one zone while India and Nepal use half and quarter hours, how Thailand set its clocks to UTC+7 in 1920, how the International Date Line bends around Kiribati and Samoa, and how summer time began in 1916 and why Europe still argues about ending it.

Who decides what time it is

How a turning planet was split into time zones.

Noon moves

Every place has its own noon.

Railway time

A timetable needs one clock.

Line zero

The world picks a starting line.

Clocks and countries

Zone lines are drawn by governments.

Where the day begins

Somewhere, the calendar has to jump.

Summer time

Moving the clock to move the day.

Read the full story as text · อ่านภาษาไทย

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