How this works

This converter uses your browser's built-in IANA time zone database — the same underlying data your operating system and every major programming language use. Rather than applying a fixed UTC offset, it looks up the actual rule that applies for the specific date and time you enter, which means it correctly handles daylight saving time transitions, historical time zone changes, and all the edge cases that a simple ±hour offset would get wrong.

How time zones actually work

Most people think of time zones as fixed offsets from UTC — "New York is UTC-5." But that's only true for part of the year. In summer, New York observes Eastern Daylight Time at UTC-4. The switchover happens at a specific moment on specific dates (the second Sunday in March and first Sunday in November in the US), and those dates change by country. Some regions have changed their DST rules, or abolished DST entirely. The IANA time zone database tracks all of this history and keeps it current.

UTC (Coordinated Universal Time)

The global reference point. All time zones are expressed as an offset from UTC. UTC itself does not observe daylight saving time and never changes.

GMT (Greenwich Mean Time)

Often used interchangeably with UTC in casual contexts, though technically GMT is a specific time zone (the UK in winter) while UTC is a time standard. For most purposes the distinction doesn't matter.

Daylight Saving Time

A practice of advancing clocks by one hour in spring and reverting in autumn, to shift usable daylight into evening hours. Observed by most of the US, Canada, Europe, and some other regions. Not observed in most of Africa, Asia, Japan, China, India, or the state of Arizona.

IANA time zones

The formal database of named time zones used by computing systems worldwide (e.g. "America/New_York", "Europe/London", "Asia/Tokyo"). Each entry encodes the full history of that region's offset rules. This is the data source underlying this converter.

Common use cases

Scheduling international calls or meetings

Enter the planned meeting time in your local zone, select the participant's zone as the target, and confirm what time it falls for them. Critical around DST transition dates when offsets temporarily differ from their usual values.

Decoding a timestamp from another region

When a log file, message, or document shows a time in an unfamiliar zone, enter it here and convert to your local time to understand when it actually occurred.

Travel planning

Check what time your flight arrives in local time, or figure out when you need to be at the airport accounting for the departure city's time zone.

Frequently asked

Does this handle daylight saving time correctly?

Yes — the conversion uses the actual time zone rule that applies on the specific date you enter, not a fixed offset. If you convert a summer date and a winter date in the same zone pair, you may see the offset change, which is correct.

Why do some cities share the same time zone option?

Time zones are defined by region and rule set, not by individual city. Nearby cities that observe identical rules are grouped under a single IANA zone identifier. For example, most of the US East Coast uses "America/New_York" regardless of whether the specific city is New York, Boston, or Atlanta.

What's the difference between UTC and GMT?

For everyday purposes, they're equivalent — both represent the zero-offset reference point. Technically, UTC is the international time standard maintained by atomic clocks, while GMT is a time zone (the UK in winter). The difference is never more than a fraction of a second.