ZeroTool Workbench

Timezone Converter

Free browser-based timezone converter. IANA database, automatic DST handling, multi-zone side-by-side comparison, shareable link. No upload.

100% Client-Side Your data never leaves your browser Free · No Sign-Up
Target timezones

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How to Use

  1. Pick a base time with the date and time picker, or click Now to use the current moment.
  2. Choose a source timezone. The tool defaults to your browser’s local zone.
  3. Add one or more target zones by typing a city name (for example tokyo) or an IANA identifier (for example Asia/Tokyo).
  4. Each target row shows the converted local time, the UTC offset, the standard or daylight abbreviation, and a DST badge when a transition is nearby.
  5. Click Share link to copy a URL that reproduces the same comparison for anyone who opens it.

Why IANA Identifiers Matter

Timezone abbreviations like PST, CST, or IST are ambiguous. CST alone can mean Central Standard Time in North America, China Standard Time, or Cuba Standard Time. The IANA timezone database removes the ambiguity by tagging every region with a continent and city — America/Chicago, Asia/Shanghai, America/Havana — and ships the full historical record of offsets and DST rules.

This tool always converts through IANA identifiers. The abbreviation shown beside each row is purely for human readability; the math runs on canonical zone names.

Daylight Saving Time and the Seven-Day Window

DST transitions matter when scheduling cross-border meetings near a spring or fall change. The tool computes the offset on the base date and again at every day in the surrounding seven days. If any nearby day reports a different offset, a DST shift badge surfaces with the day count, so a recipient pasting the link a week later still sees the correct conversion.

Zones that do not observe DST (for example Asia/Tokyo, Asia/Shanghai, most of Australia/Brisbane) display a No DST badge instead.

Shareable Links

The URL hash carries three parameters: t for the base time, s for the source zone, and z for a comma-separated list of target zones. Anyone opening the link reads the same parameters and rebuilds the comparison locally — no server is involved.

Privacy and Offline Use

Every conversion happens in your browser using Intl.DateTimeFormat. No times, zones, or links are sent to a server. The page works offline once it has loaded; you can keep the tab open while travelling without service.

FAQ

How does this tool handle Daylight Saving Time?

It uses your browser's IANA timezone database through Intl.DateTimeFormat. DST shifts apply automatically based on the date you enter — historical and upcoming transitions both work. A DST badge appears when your base time sits within seven days of a DST boundary in any displayed zone.

Why does my converted time differ from another timezone tool?

Different tools may ship older tzdata or apply DST rules incorrectly for historical dates. This converter relies on the IANA tzdata bundled with your browser, refreshed with each browser release. Edge cases include retroactive changes such as Brazil's 2019 DST abolishment or Russia's 2014 zone reset.

Can I share a converted result with someone in another timezone?

Yes. Click Share link — the URL hash encodes your base time, source zone, and the list of target zones. Anyone you send the link to opens the same conversion regardless of their local time.

Does this work offline?

Yes. After first load the page never calls the network for time data. Conversions run entirely in your browser using built-in Intl APIs.

What if my browser doesn't support Intl.supportedValuesOf?

The tool falls back to a curated list of around 60 widely used IANA zones such as Asia/Tokyo and America/New_York. Browsers older than mid-2022 may hit this fallback; conversions still work but the search list is shorter.