Could daylight-saving changes affect a timeline?¶

Yes. A forward clock change omits a local hour and a backward change repeats one, making local times missing, duplicated or apparently out of sequence.

Offset information resolves much ambiguity¶

UTC storage avoids repeated absolute time, but conversion, local-only devices and exports without offsets reintroduce it. Two identical local clock values can be an hour apart, and a value during the skipped interval may be impossible under that zone's rules.

Apply the historical transition rule¶

Preserve original value and offset and identify storage and display zones. Check whether the event date was near a transition in the relevant jurisdiction and use a recognised date-specific rule.

If a repeated-hour value lacks an offset, report ambiguity unless UTC or an independent reference resolves it.