Time Zone Converter
Convert any time across multiple zones at once. No accounts, no tracking.
What this tool does
Converts a single moment (date plus time in a source zone) into the equivalent local
time across one or more target zones. Hold Ctrl (Cmd on Mac) to select multiple
target zones at once. The math uses the browser's built-in Intl.DateTimeFormat
and time-zone database, so it correctly handles daylight saving transitions and
historical changes per IANA. Nothing is uploaded; the calculation is local.
How to use it
Pick a date and a time. Pick the source time zone (defaults to your browser's local zone). In the target list, click to select; Ctrl-click or Shift-click to select multiple. Press Convert. The output shows each target's local time and a day-offset (-1, 0, or +1) so you can see at a glance whether the meeting is yesterday or tomorrow elsewhere. Press Use current time to fill the date and time with right-now in the source zone.
Common use cases
- Scheduling a meeting across distributed teams without picking up a calendar app.
- Confirming when a livestream or product launch starts in your local time.
- Coordinating with international clients (UK, EU, India, Japan, Australia).
- Converting a deployment cutover time announced in UTC into your team's working hours.
- Reading a bug report's timestamp into your local time without doing arithmetic by hand.
Common pitfalls
- Daylight saving day. On the day a region changes between standard and daylight saving time, "9am local" can be ambiguous (skipped or repeated hour). The tool uses the browser's interpretation, which is usually right but worth double-checking on transition days.
- City names vs IANA zones. "London" is
Europe/London; "New York" isAmerica/New_Yorknot "EST" (Eastern is sometimes Standard Time, sometimes Daylight Time, depending on date). Use the IANA zone names in the dropdowns. - Browser timezone database lag. A tiny number of regions change DST rules unexpectedly (Egypt did in 2023, several others in recent years). Most browsers update within months; if you are converting around a fresh policy change, verify against an authoritative source.
Frequently asked questions
- Why is "EST" not in the dropdown but "America/New_York" is?
- Three-letter zone abbreviations like EST are ambiguous: EST means Eastern Standard Time in the US, but the same abbreviation is reused by other regions, and large parts of the US switch between EST and EDT for daylight saving. IANA zone names (America/New_York, Europe/London, Asia/Tokyo) identify a region whose time policy has been consistent over its history, so the conversion handles daylight saving correctly without ambiguity.
- How does this handle daylight saving transitions?
- The browser Intl.DateTimeFormat uses the IANA time zone database, which encodes every region DST history and current rules. The tool delegates to it. On a transition day ("spring forward" or "fall back"), the result matches what the browser would produce for any other time-zone math, which is correct for almost every case but can be ambiguous on the exact transition hour.
- What if I need historical times before the IANA database existed?
- For dates more than ~50 years ago, IANA assigns an estimated offset based on documented standard time at that location. Pre-railway times (mid-1800s and earlier) had no standardized zones at all, so any conversion is conventional. For modern day-to-day work this never matters; for historical research, verify against an authoritative source for the year and place in question.
- Is my chosen meeting time saved or shared anywhere?
- No. The tool runs locally in your browser. Nothing is uploaded, stored, or sent to any server. Refreshing the page resets all selections.
- Why does the day-offset show "+1 day" or "-1 day"?
- When you convert across distant zones (US West Coast to East Asia, for example), the local date in the target zone is often different from the source date. The +1 or -1 offset shows that at a glance, so a meeting "Tuesday 5pm Pacific" reads correctly as "Wednesday 9am Tokyo" instead of looking like Tuesday in Tokyo column.
- Can I convert a duration (like a 2-hour meeting) instead of a single moment?
- Not directly. Pick one end of the meeting and convert that moment. The duration itself is identical in every target zone (zones do not bend duration, only display). If you need to confirm a meeting fits inside working hours across all participants, convert both start and end and compare to each region working day.
Cite this tool
For academic, journalistic, or technical references. Pick a format:
Citations use 2026 as the publication year. Access date is left as a fillable placeholder where the citation style expects one.