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Timezone converter

Pick a date, a time and two timezones, get the converted local time instantly.

How Timezone converter works

The timezone converter takes a date and time you enter and shows what that moment corresponds to in any IANA timezone you pick, handling daylight saving time automatically. You choose two timezones from a full list of IANA identifiers (for example, America/New_York and Europe/Paris), enter a date and time, and the converted result appears immediately. The conversion is correct for historical dates as well, because the browser's Intl API carries historical DST rule changes.

All conversion logic runs in JavaScript in your browser, using the Intl.DateTimeFormat and Temporal-compatible methods that ship with modern browsers. No date or time value you enter is sent to a server. The output is exactly what your operating system's own timezone database would compute, which is why the tool works offline once the page has loaded.

Written by Bastien Sulyan

How to use Timezone converter, step by step

  1. Select the source timezone from the first dropdown.
  2. Enter the date and time you want to convert.
  3. Select the target timezone from the second dropdown.
  4. Read the converted date and time shown instantly.
  5. Swap the two timezones to reverse the conversion without re-entering the time.

Common use cases

  • A remote team schedules a video call by converting a proposed meeting time from US Eastern to Central European Time to confirm the slot works for all participants.
  • A developer checks what a UTC timestamp from a server log corresponds to in Tokyo local time to trace a bug in a time-sensitive workflow.
  • A traveler planning an international flight converts the departure time listed in local airport time to their home timezone to know what time to set an alarm.
  • A content manager scheduling a social-media post converts the target publication time from their local timezone to UTC for accurate scheduling in the platform's settings.

Frequently asked questions

How does the tool handle daylight saving time?

The browser's Intl API carries the full IANA timezone database, including historical and current DST rules for every region. When you enter a date, the tool applies the rule that was in effect on that specific date in each timezone. This means a summer date in New York correctly applies Eastern Daylight Time (UTC-4), not Eastern Standard Time (UTC-5).

What timezone identifiers does the tool accept?

Full IANA timezone identifiers such as America/New_York, Europe/Paris, Asia/Tokyo, Australia/Sydney, and UTC. The dropdown lists every identifier recognized by your browser's Intl implementation, which covers the full IANA database.

Can I convert historical dates before DST rules changed?

Yes, within the coverage of the IANA database. The database contains historical timezone offset changes for most regions going back to the early 20th century. For very old dates (before roughly 1900) coverage varies by region.

Is the date and time I enter sent to a server?

No. The conversion is done by the Intl.DateTimeFormat API built into your browser. Your input never leaves the tab. You can verify this by opening the browser's Network panel while using the tool: no request is sent for any conversion.

What happens when a clock change makes a time ambiguous or nonexistent?

When clocks spring forward, one hour of local time is skipped (those times do not exist). When clocks fall back, one hour of local time occurs twice (those times are ambiguous). The Intl API resolves ambiguous times using the UTC offset that was in effect before the transition. If you enter a nonexistent time, the tool will typically shift it forward to the next valid time.

Does the timezone converter work offline?

Yes, once the page has loaded. The conversion is arithmetic over the IANA rules bundled inside the browser, so no network connection is needed afterward. Disconnect from the internet and try a conversion: the result will appear as normal.

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