One local time, two instants
At 02:00 EDT on 3 November 2024, New York clocks went back to 01:00 EST. Every time from 01:00 to 01:59 that night happened twice: first at UTC−04:00, then an hour later at UTC−05:00. 01:30 is therefore either 05:30 UTC or 06:30 UTC.
Most converters silently pick one. This one shows both candidates and waits for a choice, or applies the policy you set: earlier, later, the calendar default (RFC 5545 and Temporal both use the earlier instant), or reject.
Local times that never happen
On 10 March 2024 New York clocks jumped from 02:00 straight to 03:00. 02:30 did not exist. You can move it forward (03:30 EDT, the usual calendar behaviour), move it back (01:30 EST), or refuse to convert. Try it by changing the date above.
Some transitions are not one hour. Lord Howe Island shifts by 30 minutes, and Samoa skipped the whole of 30 December 2011 when it moved across the date line.
Searching for a zone
Type a city (“Pune”), an IANA identifier (“Europe/Berlin”), a legacy name (“Asia/Calcutta” resolves to Asia/Kolkata), an offset (“+05:45”) or an abbreviation. Abbreviations always open a choice, because the same letters name different places.