When the clock skips. Or repeats.

Most deadline conversions are straightforward. Clock changes create two exceptions: a local time that never happens, and a local time that happens twice. Guessing can shift a sale reminder by an hour or more. FanWindow asks you to resolve the exception before sharing.

A skipped time has no matching instant

In a typical spring clock change, a region jumps forward. Under the currently published America/New_York rules, 8 March 2026 goes from 01:59 to 03:00. Entering 02:30 on that date describes a clock time that does not exist there.

Some software silently moves such a time forward. FanWindow rejects it. Check the original notice, including its time-zone label. The organizer might have meant a different zone or made a typo. Choose a corrected time only after you have enough information. The tool cannot determine what the organizer intended.

A repeated time needs an offset

When clocks move backward, the same clock reading can correspond to two instants. Under those same rules, 1 November 2026 at 01:30 in New York occurs first at UTC−04:00, then at UTC−05:00. The first is 05:30 UTC; the second is 06:30 UTC.

FanWindow shows both occurrences with their UTC offsets and requires you to choose. “First” and “second” describe chronological order, not which one is more likely correct. If the notice gives only a time and region, ask the organizer to clarify. Do not select an offset simply to get past the form.

Not every change is one hour

Clock rules belong to governments, and changes do not always follow the one-hour pattern many people expect. Regions may use half-hour changes, discontinue seasonal adjustments, or change their standard offset. A mental shortcut based on last year’s concert can fail this year.

FanWindow uses the Temporal polyfill with your environment’s regional time-zone data. It compares the earlier and later interpretations of a local time, rejects gaps, and requires a choice for overlaps. It does not assume a transition lasts one hour.

Your local clock can change too

A concert in Seoul may keep the same Korean time while its time in your city shifts between summer and winter. A display-zone change is safe because FanWindow retains the event’s UTC instant. But a future government rule change can make old calculations inaccurate; keep your device updated and recheck the official source close to the date.

A practical verification routine

1. Copy the complete source date, clock time, and zone label
2. If the tool rejects the time, return to the notice rather than shifting it yourself
3. If two offsets appear, find an explicit offset or clarification from the organizer
4. Preview in the source zone and at least one recipient zone before sharing