Timezone Converter
Pick a date, time, and source timezone. Compare it against 3-4 other zones at once, computed with the
browser's native Intl timezone data.
Private by architecture:
All processing is 100% client-side memory. Your data never leaves this browser tab.
Source Time & Zone
Compare in
About This Tool
Enter a date, time, and source timezone once, then compare the equivalent clock time in up to several other IANA timezones at the same time. Every conversion runs through the browser built-in Intl.DateTimeFormat, so DST transitions and historical offset rules are handled by the same timezone database your OS already ships: no bundled, potentially stale tz data.
The timezone list is populated from Intl.supportedValuesOf("timeZone") when the browser supports it, falling back to a curated list of ~30 major zones otherwise.
Key Features
- Full IANA zone list: Every timezone your browser recognizes, via Intl.supportedValuesOf, with a hardcoded fallback for older engines.
- Compare multiple zones at once: Add as many target timezone rows as you need.
- Native Intl formatting: Each result uses medium date and long time styles, including the zone abbreviation/offset.
- Live recompute: Changing the date, time, source zone, or any target zone updates every row immediately.
- Remove rows: Drop a comparison zone you no longer need.
- Defaults to now: Opens pre-filled with the current date/time in your local zone.
Frequently Asked Questions
Where does the timezone list come from?
From Intl.supportedValuesOf('timeZone'), the browser's own IANA timezone database. If that API isn't available, a hardcoded list of about 30 major zones is used instead.
Does this account for Daylight Saving Time?
Yes. Because conversion goes through Intl.DateTimeFormat with the real zone name (not a fixed UTC offset), DST rules for that specific date are applied automatically.
How many comparison timezones can I add?
As many as you like: click "Add another timezone" repeatedly. Three or four at once is typical for comparing team members across regions.
What timezone is used if I don't change anything?
The "From timezone" defaults to your browser's local timezone, and the date/time field defaults to the current moment.
Is any date or time data sent to a server?
No. All conversion happens in your browser using the native Intl API.
