What is UTC?
UTC is Coordinated Universal Time. It is the time standard that every time zone is measured from.
UTC stays the same all year. It never changes for daylight saving time, even when the clocks around it do.
How to read UTC+ and UTC-
A time zone is written as its difference from UTC.
Tokyo is UTC+09:00, so its clocks are 9 hours ahead of UTC. New York's standard time is UTC-05:00, 5 hours behind UTC.
When New York moves its clocks forward for summer, it becomes UTC-04:00. The zone moves. UTC does not.
The page on the time zone of each US state gives the winter and summer times for each US zone, such as EST and EDT.
The clocks furthest behind UTC are at UTC-11:00, in Pago Pago, American Samoa and in Niue. The clocks furthest ahead are at UTC+14:00, in Kiritimati, Kiribati. Every offset in between is in the time zone chart.
Is UTC the same as GMT?
For telling the time, yes. GMT and UTC show the same clock time.
They are different kinds of thing. GMT is the name of a time zone. UTC is the standard that every time zone, GMT included, is measured from.
The difference shows in summer. London keeps GMT in winter. In summer it moves to BST, 1 hour ahead of GMT. UTC stays where it was.
On this site, 7 time zones use GMT as standard time. Only 2 of them change their clocks in summer.
| Time zone | Used in | In summer |
|---|---|---|
| London | United Kingdom, Guernsey, Isle of Man, Jersey | BST, UTC+01:00 |
| Dublin | Ireland | IST, UTC+01:00 |
| Abidjan | Ivory Coast, Burkina Faso, Ghana, Gambia, Guinea, Iceland, Mali, Mauritania, Saint Helena, Ascension and Tristan da Cunha, Sierra Leone, Senegal, Togo | Stays on GMT |
| Bissau | Guinea-Bissau | Stays on GMT |
| Monrovia | Liberia | Stays on GMT |
| Sao Tome | São Tomé and Príncipe | Stays on GMT |
| Danmarkshavn | Greenland | Stays on GMT |
Why the letters are UTC, not CUT
The letters do not follow the English words, and that was deliberate.
In English, the short form would be CUT. In French, where the name is temps universel coordonné, it would be TUC.
The International Telecommunication Union wanted one short form for every language. It chose UTC, which follows neither.
Where you see UTC
Aviation, shipping and the military often write UTC as Z, spoken as Zulu. A time written as 14:00Z means 14:00 UTC.
UTC is also the safe way to record when something happened. Where clocks go back for winter, one local hour happens twice. A record kept in local time cannot tell those two hours apart. UTC never goes back, so every moment has its own time.
The clock on this site works the same way. The server sends the time in UTC, and your browser turns it into the local time you see. You can check your own clock against that server.
Every code the site prints beside a time, and the ones that mean different things in different places, are listed in the time zone abbreviations register.
UTC is always written on the 24-hour clock. The guide to AM and PM shows how to convert.
Common questions
Does UTC change for daylight saving time?
No. UTC stays the same all year. When a place moves its clocks forward or back, its difference from UTC changes, but UTC itself does not.
What does UTC stand for?
UTC stands for Coordinated Universal Time. The letters follow neither the English nor the French name, so one short form works in every language.
Is GMT the same as UTC?
GMT shows the same clock time as UTC, but GMT is a time zone and UTC is a standard. The United Kingdom uses GMT only in winter, and some countries use it all year.
What is Zulu time?
Zulu time is another name for UTC. Aviation, shipping and the military write it as a Z after the time, as in 14:00Z.
Sources
We checked each fact on this page against these sources on 30 September 2026. Times, offsets and clock changes come from the time zone database.