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Global ClockTime zone converter & meeting planner
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AUTO follows the operating system. Working hours drive the green banding on every grid. All four persist on this device only.

How UTC offsets work

Every clock on earth is described as a distance from one reference clock. Get that idea and the rest of this site reads itself.

One reference clock

Coordinated Universal Time — UTC — is the clock everything else is measured against. It never changes for daylight saving and it belongs to no country. A local time is written as UTC plus or minus a number of hours: Berlin in August is UTC+2, New York is UTC−4. Subtract one from the other and you have the gap between them, six hours in that example.

An offset is a fact about a moment, not a place

Berlin is UTC+2 in August and UTC+1 in January, so “Berlin is UTC+2” is only true of part of the year. This is why the planner asks for a date before it shows you a grid: the honest answer to “how far apart are we?” depends on the day you mean.

Not every offset is a whole hour

Half-hour and quarter-hour offsets are ordinary. India is UTC+5:30, Nepal UTC+5:45, parts of Australia UTC+9:30. Right now 8 of the zones we track sit on an offset that is not a whole number of hours. Any tool that assumes whole hours will be thirty minutes wrong for about a fifth of the world’s population — so nothing here rounds.

Abbreviations are not identifiers

CST is Central Standard Time in Chicago, China Standard Time in Shanghai and Cuba Standard Time in Havana. Abbreviations are for reading, never for storing. The unambiguous name is the zone identifier — Europe/Berlin, America/New_York — which is what this site keeps internally and what you should keep in your own systems. Where a zone has no accepted letters at all, the database publishes the numeric form and so do we: Dubai reads UTC+4, not an invented “GST”.

If you take one rule away: store the instant in UTC and the zone identifier separately, and convert only when you display. Storing “3pm CST” loses the information you will need later.

In practice

Read the offset for the date in question, not for today. Write times with the zone attached. Assume nothing about whole hours. Expect the gap between two cities to change two to four times a year.

Try it on the planner →Put two cities on one timeline and watch the offset resolve for the date you pick.Daylight saving explained →Why the gap between two cities moves, and the weeks it goes strange.IANA time zone notes →Where our offsets come from and how often they change.