How it works
We treat the input as a wall-clock time in the source zone, convert it to a UTC instant using Intl.DateTimeFormat, then format that instant in each target zone. DST transitions are handled correctly by the browser's built-in tz database.
FAQ
Does it handle daylight saving time? Yes. We use the browser's built-in Intl.DateTimeFormat with the IANA time-zone database, which knows historical and current DST rules for every zone.
Why are the time-zone names so long? IANA names ("America/New_York", "Asia/Seoul") are the unambiguous canonical identifiers used by every modern operating system and browser. Abbreviations like "EST" or "BST" are ambiguous (e.g. BST is both British Summer Time and Bangladesh Standard Time).
Can I schedule across more than 4 zones? This tool fixes 4 outputs to keep the UI readable. For complex multi-zone scheduling, dedicated apps like Worldtimebuddy are better.