How to use
Choose the date and a 24-hour local time, then select the source and destination time zones. Both dropdowns stay available after any selection. Their list uses your browser’s IANA data. Calculate confirms the instant; changing a zone afterward updates that result until you edit the date or time. The initial date is today in UTC.
Method and interpretation
A time zone is a set of date-dependent rules, not a fixed offset. America/New_York and Europe/London may change offsets on different dates. This tool uses the browser’s Intl data for the selected date. The date-change value compares the two local calendar dates, not elapsed travel time.
Examples
2026-01-15 at 12:00 in UTC is 17:30 in Asia/Kolkata and 17:45 in Asia/Kathmandu. Converting 2026-01-01 at 00:30 in Asia/Tokyo to America/Los_Angeles gives 2025-12-31 at 07:30. To check the reverse direction, enter the displayed target date and time and exchange the two zone names.
Limits and errors
During a spring DST jump, a clock time may never occur; the tool returns an error instead of moving it forward. In autumn, a time may occur twice. The error lists the actual UTC candidates: choose earlier or later, then calculate again. For New York, 2026-03-08 02:30 is absent and 2026-11-01 01:30 is repeated.
Frequently asked questions
Why can another device disagree?
Browser time-zone data versions can differ, especially after rule changes. This tool cannot guarantee every historical or future rule. Invalid dates and unsupported zone names are rejected. Editing clears the previous result. Clear empties the input fields; no calendar account, booking or reminder is created.