Time zones: every UTC offset, and what the abbreviations mean

Every clock in the world is UTC plus or minus an offset. Right now 37 distinct offsets are in use across 420 named zones — 11 of them are not whole hours. Below is each offset with the places on it, and a table of the abbreviations that mean two different things depending on who wrote them.

Every offset in use

Sorted by offset rather than alphabetically, because that is the question people actually have. The set changes twice a year: when the northern hemisphere moves onto daylight saving, zones shift up an hour and the grid rearranges. These were computed when this page was last built.

The offsets that are not whole hours

Offsets are political, not geometric. 11 of the 37 in use are off the hour — most by 30 minutes, three by 45. Nepal chose UTC+05:45 to sit a quarter-hour clear of India. The Chatham Islands run 45 minutes ahead of New Zealand. Eucla, population under a hundred, has its own offset because the nearest towns in either direction are hours away.

What the abbreviations mean

6 of the abbreviations below mean more than one thing. IST is three different countries up to four and a half hours apart; CST is the central United States, all of China, and Cuba. A calendar invite that says “3 PM IST” is a real way to miss a call by half a day, so where it matters, write the UTC offset instead of the letters.

Need the arithmetic done for you instead? The converter takes two cities and applies the right offset for the date, daylight saving included.

Frequently asked questions

How many time zones are there?

There are 38 hourly and sub-hourly UTC offsets defined, but not all are in use at once — the number in use changes twice a year as the northern and southern hemispheres move on and off daylight saving. The IANA database, which every operating system uses, lists over 400 named zones, because a "zone" is a region with a shared history of clock changes rather than a slice of the map.

What does IST mean?

It depends who wrote it. IST is India Standard Time (UTC+05:30), Israel Standard Time (UTC+02:00) and Irish Standard Time (UTC+01:00). A meeting invite that says "3 PM IST" is ambiguous by up to four and a half hours, which is why UTC offsets are safer than letters.

Why are some offsets not whole hours?

Because offsets are political, not geometric. India, Iran, Afghanistan, Myanmar, parts of Australia and Newfoundland all sit on 30-minute offsets, and Nepal (UTC+05:45), the Chatham Islands (UTC+12:45) and Eucla in Australia (UTC+08:45) use 45-minute ones. Each was chosen to put local noon near the middle of the day for the population that mattered.

What is the difference between UTC and GMT?

UTC is the atomic time scale used for civil timekeeping worldwide. GMT is the United Kingdom's winter time zone, which happens to show the same clock time as UTC. They coincide, but they are not the same kind of thing — for anything precise, say UTC.

Which time zone is UTC+0?

In winter it covers the United Kingdom, Ireland and Portugal, along with Iceland and much of West Africa which stay there all year. In summer the UK, Ireland and Portugal move to UTC+01:00, so the set of places at UTC+0 is different in July than in January.

Related

Current time by city · 2026 and 2027 clock-change dates · Where exact time comes from · Plan a meeting across zones

Times on this page were calculated on 11 September 2026.