Time zones – how they work
The Earth is divided into time zones so the clock roughly follows the sun wherever you are.
What is a time zone?
A time zone is an area where everyone uses the same clock time. The Earth turns 360 degrees in 24 hours, which is 15 degrees per hour. In theory that gives 24 zones, each one hour wide. In practice the borders follow countries and regions, so zones have irregular shapes, and some are offset by half or a quarter of an hour, such as India (UTC+5:30) and Nepal (UTC+5:45).
What is UTC?
UTC, Coordinated Universal Time, is the reference that all time zones are counted from. It is kept by atomic clocks and never changes for daylight saving. UTC+1 means the clock is one hour ahead of UTC. Older texts often say GMT, Greenwich Mean Time, which in everyday use is the same as UTC.
Which time zone does Sweden use?
Sweden uses Central European Time, CET, which is UTC+1. In summer it uses Central European Summer Time, CEST, which is UTC+2. The same time is used in Norway, Denmark, Germany, France and Spain, among others. Finland is one hour ahead of Sweden and the UK one hour behind.
The date line
The International Date Line runs through the middle of the Pacific Ocean. Travel west across it and you skip a day; travel east and you get the same date twice. That is why Kiribati and Samoa are among the first to celebrate New Year, while American Samoa, a few hundred kilometres away, is among the last.
Common time zones
| Time zone | Offset | Examples |
|---|---|---|
| CET / CEST | UTC+1 / UTC+2 | Stockholm, Berlin, Paris |
| EET / EEST | UTC+2 / UTC+3 | Helsinki, Athens |
| GMT / BST | UTC+0 / UTC+1 | London, Dublin |
| EST / EDT | UTC−5 / UTC−4 | New York, Toronto |
| JST | UTC+9 | Tokyo |