Timezone converter — any date/time to multiple cities at once
Pick a date/time and source IANA timezone, then see the equivalent local time in many target timezones at once, with UTC offsets and ±day badges for date rollovers. Handy for cross-border meeting scheduling, deadline translation, and DST-aware comparisons. Runs entirely in your browser via the Intl API.
How to use
Pick a source timezone and a date/time. The target list shows what local time that instant maps to in each target TZ, with UTC offset and a ±day badge for date rollovers. Press Now to reset the source to the current instant, or Sample to load a representative cross-timezone time. Add or remove target timezones by IANA name (Asia/Tokyo, America/New_York, Europe/London, ...). DST is automatically handled by the browser's Intl API.
FAQ
- Is the date/time uploaded anywhere?
- No. All math runs in the browser's Intl API; nothing leaves your device. Safe for meeting-time triangulation with confidential calendars.
- How is this different from the world-clock tool?
- world-clock is a live multi-clock face — useful for monitoring several timezones at once. timezone-convert is a one-shot converter: pick a source TZ, type a specific instant, see the rest of the world. The target rows surface day rollovers explicitly and the source TZ is always front-and-center.
- Does it handle Daylight Saving Time (DST)?
- Yes. The browser's IANA tz database does the heavy lifting. Non-existent local times (e.g. 02:30 on a DST 'spring forward' day) are snapped to a nearby valid instant per the browser's rules.
- Which timezones are supported?
- Anything Intl.supportedValuesOf('timeZone') returns — i.e. the full IANA tzdb. Modern Chrome/Edge/Safari/Firefox cover hundreds of zones. If your browser does not expose supportedValuesOf, you can still type the IANA name directly into the add field.
- How is the ±day badge computed?
- By comparing the local date in the source TZ to the local date in each target TZ. e.g. Tokyo (Asia/Tokyo) at 2026-03-15 09:00 maps to Los Angeles (America/Los_Angeles) at 2026-03-14 17:00, so LA gets a '-1 day' badge.
- I want to use UTC as the source
- Pick UTC in the source timezone dropdown and enter the time. The targets will show how that UTC instant lands in each local TZ.
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