Zones, not abbreviations
Abbreviations such as IST or CST are ambiguous: IST is India, Ireland and Israel, and CST is US Central, China and Cuba. This grid uses IANA identifiers (Asia/Kolkata, America/Chicago) and shows the abbreviation only as a label. Offsets come from the IANA tz database bundled in your browser, so they include historical changes and zones with unusual offsets, such as Nepal (+05:45) and the Chatham Islands (+12:45/+13:45).
Planning across daylight-saving changes
The grid marks zones whose offset differs from their offset six months earlier, which shows whether daylight saving time is in effect. In the last week of October, Europe has fallen back but the US has not yet. The New York to London gap is then four hours instead of five, which often moves recurring meetings. Use the Calculator tab to add calendar days in a zone and see where the offset changes.
Questions
- Where does the time-zone data come from?
- From your browser's Intl API, which ships the IANA tz database. Browsers update it with their releases, so very recent government changes may lag until your browser updates.
- Can I search for a city?
- Search by any part of the IANA identifier, for example "Kolkata", "Paris" or "Sao_Paulo". Cities that share a zone use one representative identifier.
- Does this work offline?
- Yes, once the site has been loaded and installed. Zone rules are in the browser itself and no server is involved.