Timezone Converter

Examples

Results from the converter’s own functions:

The second group shows why a fixed “London is five hours ahead of New York” rule fails: the United States moves its clocks on the second Sunday of March and the United Kingdom on the last Sunday, so for about three weeks in March the gap is four hours. The tool gives the right answer because it uses each zone’s rules for that exact date, not a stored offset.

Times That Do Not Exist or Happen Twice

On a spring-forward night the clock skips an hour. In New York on 2026-03-08 there is no 02:30; the tool reads it as 03:30 EDT (2026-03-08 03:30:00, UTC-04:00 (EDT) in the New York row, 2026-03-08 07:30:00, UTC+00:00 in the UTC row), the same choice as RFC 5545 for calendar times and the “compatible” option of JavaScript’s Temporal proposal. On a fall-back night an hour repeats: 2026-11-01 01:30 in New York happens twice, and the tool takes the first one, 01:30 EDT (2026-11-01 05:30:00, UTC+00:00). If you mean the second occurrence, enter the time in UTC instead.

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 on some rows is for reading only; the conversion uses the zone name.

Daylight Saving Time and the Seven-Day Window

DST transitions matter when you schedule meetings near a spring or fall change. The tool looks for an offset change in the target zone within seven days before or after the base time and counts the calendar days, in that zone, between the base date and the date of the change. The row shows DST shift in n day(s) or DST shifted n day(s) ago, or DST shift today / DST shifted today when the change falls on the base date, a reminder that the same meeting time will convert differently on the other side of the change. For example, London changes on 2026-10-25, so a base time that is 2026-10-29 in London shows DST shifted 4 day(s) ago.

Zones that do not observe DST in that year (for example Asia/Tokyo, Asia/Shanghai and Australia/Brisbane) show a No DST badge instead. The tool decides this by comparing the offsets on 15 January and 15 July of the base year; an offset change within the seven days still shows its own badge, as for Africa/Casablanca, which leaves UTC+01:00 for Ramadan on 2026-02-15 although its January and July offsets match.

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. The tool rewrites them in the address bar after every change, not only when you click Share link. Anyone opening the link reads the same parameters and rebuilds the comparison locally — no server is involved. Zone names that the other person’s browser does not recognize are left out.

Limitations

• Abbreviations come from the browser’s English (Canada) locale data, which has them only for North American zones (EST, PDT, AKST and similar). JST, CET or IST are not shown; the UTC offset is always shown.
• The search list comes from Intl.supportedValuesOf(‘timeZone’), which lists one name per zone and differs between engines: Chrome 152 lists Asia/Calcutta and Europe/Kiev rather than Asia/Kolkata and Europe/Kyiv, and has no UTC entry. All of these names work when typed.
• The time zone data is the browser’s copy. If a government changes its rules at short notice, results for future dates can be wrong until the browser updates.
• The search box takes English city names (tokyo, new york, mumbai), UTC and IANA names. Case does not matter. A partial name needs at least three characters, must start a word of the city name and must fit one zone only: york finds America/New_York, while san (San Juan, Santiago and others) is rejected. Time zone abbreviations such as EST, ist or JST are rejected too (EST and IST each name several regions); all three cases show “Unknown timezone. Enter a city or an IANA name.”
• Seconds are kept when the base time has them; there is no working-hours grid or meeting planner view.
• Your targets and source zone are remembered in this browser’s local storage; the base time is not, although it stays in the address bar after # and in the browser history. For Unix timestamps, use the Timestamp Converter.