Time zone converter

A time zone is more than a fixed offset

IANA zone names such as America/Chicago carry regional clock rules, including daylight-saving transitions. The converter uses the browser’s built-in time-zone database for the selected date. This is more reliable than assuming that Chicago is always UTC−6 or London is always UTC+0.

Repeated times are reported

When clocks move backward, a local time such as 1:30 AM may occur twice with two different UTC instants. If the entered time is ambiguous, this tool deliberately uses the earlier occurrence and says so in the result. Confirm which occurrence applies before scheduling travel, system jobs, trades, or legal deadlines.

Skipped times are rejected

When clocks move forward, part of the local clock may not exist. Rather than silently changing a nonexistent 2:30 AM into another time, the calculator asks for a valid time before or after the transition. This avoids a subtle but common scheduling error.

Rules can change

Governments can revise time-zone and daylight-saving policy. Results depend on the time-zone data shipped with the current browser or operating system. For critical future events, verify the conversion with the organizer, carrier, exchange, or other authoritative schedule close to the event.

This tool covers the listed IANA regions and chooses the earlier occurrence of a repeated local time. It does not replace an authoritative timetable or guarantee future government clock rules.