World Clock

How time zones work

Earth turns 360 degrees in 24 hours, so every 15 degrees of longitude is roughly one hour. Time zones follow that idea but are drawn along borders and political decisions — China uses a single time (UTC+8) across the whole country, the contiguous US has four main zones, and places like India and Nepal use half- or quarter-hour offsets.

UTC vs GMT

UTC (Coordinated Universal Time) is the atomic-clock standard every time zone is defined from. GMT is a time zone based on Greenwich, used by the UK in winter. They show the same time day to day, but UTC never shifts for daylight saving.

Daylight saving time

In Europe clocks go forward on the last Sunday of March and back on the last Sunday of October. The US and Canada change on the second Sunday of March and the first Sunday of November. In the southern hemisphere (Australia, New Zealand, Chile) summer time runs from about October to April. Each city page shows the exact date of its next clock change.

UTC offsets by city

Frequently Asked Questions

How many time zones are there in the world?
There are 24 main time zones of 15 degrees each, but half- and quarter-hour offsets such as India (UTC+5:30), Nepal (UTC+5:45) and Iran (UTC+3:30) mean more than 35 different local times are in use.

What is the largest time difference on Earth?
The furthest-ahead time is UTC+14 (Line Islands, Kiribati) and the furthest-behind is UTC−12 (uninhabited Baker and Howland islands) — a 26-hour spread, so two different calendar dates can exist at once.

What is the difference between UTC and GMT?
GMT is a time zone (used by the UK in winter); UTC is the atomic-clock time standard that all time zones are defined from. In everyday use they show the same time, but UTC never changes for daylight saving.

Which countries use daylight saving time?
The EU, the UK, most of the US and Canada, south-eastern Australia, New Zealand and Chile, among others. Most of Asia and Africa, as well as Türkiye and Russia, do not.