World clock

Add a city such as Berlin or an IANA zone such as America/New_York. Suggestions come from your browser; an ambiguous city needs its full zone. UTC is also available. Up to 24 unique zones are saved locally; × removes a card.

All cards show the same instant, with the local date and current UTC offset. The selected page language controls dates. Daylight saving time follows the browser’s timezone database. Midnight is 00:00, never 24:00.

The device clock is used initially. Sync internet time explicitly requests an approximate time through this site’s PTB HTTPS-Date endpoint, then worldtimeapi.org if necessary. Network latency and whole-second HTTP headers limit accuracy; this is not an NTP or atomic-clock measurement. The request ends after ten seconds. A failure preserves the previous clock. Device clock cancels a pending request and removes the correction.

Only the zone list survives reload. A time correction stays within the current page session, is not restored from an old cookie, and is limited to one day. No automatic network requests; timestamps and zones are not sent as inputs. Browser and device sleep can delay drawing; the next update uses the current time.