Why do you call these IANA time zones?

IANA maintains the tz database, the canonical list of zone identifiers such as Europe/London used by operating systems and programming languages. Naming a zone by city avoids the ambiguity of abbreviations like CST.

Do the offsets include daylight saving time?

The offsets shown are the standard (winter) offset. Many zones move forward an hour in summer for daylight saving, so the live offset can differ for part of the year.

Is the lookup done on a server?

No. The zone list is bundled with the page and all searching happens in your browser.

What does an identifier like Asia/Kolkata mean?

It is a Region/City pair from the tz database. The region groups by continent or ocean, and the city is a representative location whose historical and current rules define the zone.

Why not just use abbreviations like EST or CST?

Abbreviations are ambiguous — CST can mean Central US, China, or Cuba time. IANA Region/City names are unique and carry the full daylight-saving history, which is why software uses them.

Can I search by UTC offset?

Yes. Type an offset such as +05:30 or -08:00 to find zones at that standard offset, alongside searching by city or region.

Where can I use these identifiers?

Anywhere that accepts an IANA zone — JavaScript Intl and Date, Python zoneinfo, Java, cron and server configs, and calendar apps. Copy the exact Region/City string.

Time Zone List Reference

IANA time zone list

This reference lets you look up the canonical IANA time zone identifiers — the Region/City names such as Asia/Tokyo and Europe/London that software uses everywhere — and their standard UTC offsets. It is for developers, sysadmins, and anyone configuring schedules, calendars, or server time zones.

How it works

The page bundles a list of zone entries, each with its IANA identifier, standard (winter) UTC offset, and a region grouping (Americas, Europe, Asia, Pacific, and so on). Your search box filters that list locally by matching against the city name, region, or offset you type. Identifiers use the Region/City convention because abbreviations like CST are ambiguous across countries, whereas a Region/City name is unique and encodes the zone’s full daylight-saving history.

Example

Searching Tokyo returns Asia/Tokyo at UTC+09:00; searching +05:30 finds Asia/Kolkata; searching Europe lists the European zones with their offsets.

IANA identifier	Standard offset
America/New_York	UTC-05:00
Europe/London	UTC+00:00
Asia/Kolkata	UTC+05:30
Asia/Tokyo	UTC+09:00

Offsets shown are the standard (winter) value; zones that observe daylight saving shift forward an hour in summer. Everything runs locally in your browser.