Time zones

Timezone Offset Calculator

Compare any two time zones on any date: their UTC offsets, the exact difference between them, the matching local time, and whether daylight saving is in force.

—Difference
—First zone offset
—Second zone offset
—Local time, first zone
—Local time, second zone
—Same moment in UTC

MonthFirst zoneSecond zoneDifference

Uses your browser's own time zone database — nothing is uploaded.

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Every zone

Hundreds of IANA zones straight from your browser's time zone database.

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Any date

Check a future meeting or a past timestamp — offsets follow the rules for that date.

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DST outlook

A twelve-month table shows exactly when the gap between two zones shifts.

How to use the timezone offset calculator

Pick two zones and a moment in time, and the offsets are worked out from your browser's time zone rules.

  1. Choose two zonesSearch the list for the cities or regions you care about.
  2. Set the date and timeThe time you enter is read as local time in the first zone.
  3. Compare the offsetsSee both UTC offsets, the difference between them and the matching local time in the second zone.

About UTC offsets

A time zone is not a fixed number of hours from UTC — it is a set of rules that says what the offset is at any given moment. Those rules change with daylight saving, and occasionally by legislation. That is why a reliable calculation always starts from a named zone such as Europe/Paris rather than a bare offset like UTC+1.

Named zones beat fixed offsets

America/New_York is unambiguous all year. UTC-5 is only correct for part of it, and silently wrong for the rest.

Daylight saving is not global

Most of Asia, Africa and South America do not observe it, so gaps to Europe and North America shift twice a year.

Half-hour and quarter-hour zones

India, Iran, Nepal, parts of Australia and Newfoundland all sit on non-integer offsets.

Rules keep changing

Countries adopt, drop and shift daylight saving regularly, which is why the IANA database is updated several times a year.

Timezone offset calculator FAQ

Questions about UTC, daylight saving and storing times correctly.

Why does the difference between two cities change during the year?

Because daylight saving does not start and end on the same date everywhere, and many countries do not observe it at all. London and New York are five hours apart most of the year but four hours apart for a couple of weeks each spring and autumn.

What is the difference between UTC and GMT?

For everyday purposes they are the same. UTC is the modern atomic-clock standard while GMT is a time zone based on the Greenwich meridian. GMT is still the legal winter time in the UK, where it becomes BST in summer.

Why do some offsets include 30 or 45 minutes?

Several regions chose partial-hour offsets to better match solar noon. India is UTC+05:30, parts of Australia are UTC+09:30, and Nepal is UTC+05:45.

Which time zone should I store timestamps in?

Store the underlying instant in UTC and store the user's IANA zone name separately. Storing a fixed offset instead breaks as soon as daylight saving rules change, which happens somewhere in the world most years.

Does this tool know about historical time zone changes?

It uses your browser's built-in IANA time zone database, which includes historical rules. Pick a past date and the offsets shown will reflect the rules that were in force then.

Explore more free tools: Time Zone ConverterWorld ClockMeeting Time Planner