Time Zone Converter
Pick a date, a time and the city it's in, then see the same moment in up to four other cities — with each zone's UTC offset and whether daylight saving time is in effect on that date.
Offsets and daylight-saving status come from the time-zone data built into your browser and operating system, which can lag behind very recent changes to a country's clock rules. Double-check against an official source before booking travel or scheduling anything time-critical.
How the conversion works
Every city in the list is an IANA time-zone name (for example Europe/London or America/New_York). Your browser's built-in Intl.DateTimeFormat accepts those names and knows each zone's history of UTC offsets and daylight-saving rules, so the converter first works out the exact instant that matches the wall-clock time you entered in the source zone, then formats that same instant in each target zone. The UTC offset shown is the difference between that zone's local time and UTC on the chosen date, so it already includes any daylight-saving shift.
- How does it know whether daylight saving time applies?
- For each zone it compares the UTC offset on your chosen date with the zone's offsets on 1 January and 1 July of the same year. If the two reference offsets are the same, the zone doesn't use daylight saving that year and the result says "no DST". If they differ, the smaller offset is treated as standard time, and the date is marked "DST in effect" when its offset matches the larger one. This works for both hemispheres — Sydney shows DST in January, London in July. The one case it can misread is a zone that permanently changes its standard offset partway through a year.
- What happens on the night the clocks change?
- When clocks go forward, a block of wall-clock time is skipped — 01:30 on the last Sunday in March doesn't exist in London. If you enter a time like that, the converter uses the moment the clocks actually reached (02:30 in that example) and tells you so. When clocks go back, a block of time happens twice; the converter uses the first occurrence and shows a note so you can add an hour if you meant the second.
- Why might a result be wrong for a very recent time-zone change?
- Time-zone rules are political decisions, and the IANA database that browsers rely on is, in IANA's words, "updated periodically to reflect changes made by political bodies". Those updates reach you through browser and operating-system updates rather than directly, so a country that changed its clocks in the last few weeks may still be shown under its old rules until your software catches up.
FAQ
Sources
Method: the page uses no time-zone tables of its own. The zone list is a curated set of IANA time-zone names; all offsets, zone names and calendar arithmetic come from the browser's Intl.DateTimeFormat with the timeZone option, read back with formatToParts. The UTC offset for a zone at a given instant is the difference between that instant's wall-clock reading in the zone and its UTC reading; daylight-saving status is inferred by comparing that offset with the zone's 1 January and 1 July offsets for the same year.
- IANA — Time Zone Database — the tz (zoneinfo) database of UTC offsets and daylight-saving rules for locations worldwide, maintained by IANA, intended for software implementers and updated as governments change their rules; this is the data browsers and operating systems ship.
- MDN — Intl.DateTimeFormat() constructor — documents that the
timeZoneoption accepts IANA time-zone names and defaults to the runtime's zone, and thetimeZoneNameoption'slong,short,shortOffsetandlongOffsetformats used to label each zone.