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.

What is the Time Zone List Reference?

Free time zone reference — search IANA time zone identifiers and their UTC offsets by city, region or offset. Runs entirely in your browser, nothing is uploaded. It runs free in your browser on Gera Tools, with nothing uploaded.

Time Zone List Reference

Name: Time Zone List Reference
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

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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.

Why IANA identifiers exist

Before the tz database was established, every operating system and application used its own timezone data in incompatible formats, with abbreviations that collided across regions (CST alone means at least three different things globally). The IANA tz database solved this by creating a single canonical list of Region/City pairs that are globally unique and carry the full history of daylight-saving changes for each location. Today, every major operating system, programming language, and calendar application uses this database internally — which is why knowing the correct IANA name is the reliable way to configure any timezone.

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.

Commonly needed identifiers

IANA identifier	Standard offset	Notes
America/New_York	UTC−05:00	US Eastern; UTC−04:00 in summer (EDT)
America/Chicago	UTC−06:00	US Central; UTC−05:00 in summer (CDT)
America/Los_Angeles	UTC−08:00	US Pacific; UTC−07:00 in summer (PDT)
Europe/London	UTC+00:00	GMT in winter, BST (UTC+01:00) in summer
Europe/Berlin	UTC+01:00	CET in winter, CEST (UTC+02:00) in summer
Asia/Kolkata	UTC+05:30	India Standard Time, no DST
Asia/Tokyo	UTC+09:00	JST, no DST
Australia/Sydney	UTC+10:00	AEST; UTC+11:00 in summer (AEDT)

Offsets shown are the standard (winter) value; zones that observe daylight saving shift forward (usually one hour) in summer.

Searching the reference

By city: type Paris to find Europe/Paris, or Lagos for Africa/Lagos
By region: type Pacific or America to list all zones in that grouping
By offset: type +05:30 to find Asia/Kolkata and Asia/Colombo; type -03:30 to find America/St_Johns (Newfoundland)

Where these identifiers are used

Once you have the correct IANA name, you can use it directly in:

JavaScript: Intl.DateTimeFormat('en', { timeZone: 'Asia/Kolkata' })
Python: zoneinfo.ZoneInfo('Asia/Kolkata') or pytz.timezone('Asia/Kolkata')
PostgreSQL: AT TIME ZONE 'Asia/Kolkata'
Linux/macOS cron: TZ=Asia/Kolkata 0 9 * * *
Calendar apps, scheduling APIs, and server configuration files

Everything runs locally in your browser — the zone list is bundled with the page and no search is sent to a server.