What is an IANA timezone identifier?

IANA timezone identifiers, also called Olson or tz database names, take the form Area/Location such as Europe/London or America/New_York. The location is a representative city for a region that shares the same offset and DST history, and these strings are the canonical way to specify a timezone in software.

Why use the IANA name instead of an offset like UTC+1?

A fixed offset cannot account for daylight saving, which shifts the offset twice a year, and it loses the historical rules a date library needs. The IANA name encodes the full set of past and future rules, so storing it lets software compute the correct local time for any date.

How is the current offset calculated?

The tool asks your browser's Intl and Date engine for the wall-clock time in each zone at this instant and compares it to UTC. Because it uses your device's up-to-date tz data, the offset reflects the current rules and the exact moment the page loaded.

What does the DST column mean?

It compares each zone's January and July offsets to detect whether it observes daylight saving at all, then checks which the current offset matches. A zone shows on (summer time) when it is currently shifted forward, off (standard time) otherwise, and no DST if it never changes.

Why do southern hemisphere zones show DST in different months?

Daylight saving follows the local summer, so the southern hemisphere shifts forward around October and back around April, opposite to the north. The tool detects DST by comparing the two offsets rather than assuming northern months, so it handles both hemispheres correctly.

Timezone Reference Lookup

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What this tool is for

This reference helps you find the correct IANA timezone identifier for a city or region and immediately see what that zone’s UTC offset is right now. It is aimed at developers configuring servers, scheduling jobs, or storing user timezones, where the canonical Olson name matters more than a raw offset.

How it works

Each timezone is named Area/Location, where the location is a representative city that stands in for everywhere sharing the same offset and daylight-saving history. To compute the live offset, the tool asks your browser for the wall-clock time in the zone at this instant and subtracts UTC, which yields the current offset in minutes.

To determine daylight-saving status, it samples the offset in January and July. If the two differ, the zone observes DST, and the larger eastward offset corresponds to summer time. The current offset is then matched against those samples to report whether the zone is on summer time, on standard time, or never changes. This comparison works for both hemispheres because it never assumes which months are summer.

Tips and notes

Always store a user’s timezone as the IANA name, not as a numeric offset, because the offset changes with DST and across history. Pass the name to a date library such as the built-in Intl.DateTimeFormat or a library like Luxon to render local times correctly. Keep your runtime’s tz data current, since governments change DST rules and offsets, and stale data produces wrong local times.