Applies to: Programme start and end labels span a daylight-saving transition.
The useful distinctions
- An offset transition can occur within a programme interval.
- Each endpoint needs its own date and offset.
- Elapsed duration follows the corresponding instants, not bare clock-label subtraction.
Treat both endpoints as complete records
An overnight schedule is easy to misread when the viewer keeps only the hour and minute. A clock change can occur between the beginning and the end. The two labels then belong to different offset contexts even though the city has not changed. Preserve the local date and offset at each endpoint. Without that information, an apparently shortened interval may be a real longer programme crossing a repeated hour.
Do the duration comparison on one timeline
Convert the start and end to UTC before subtracting them. Then compare that elapsed interval with the programme’s stated length. A difference that disappears after this conversion does not establish that material was repeated or omitted. If a discrepancy remains, report it with both endpoint records. Avoid changing the guide globally to repair an interval whose unusual appearance is explained by the transition itself.
Hypothetical worked example
In IANA 2026f, a fictional New York programme starts at 00:30 on 1 November 2026 with offset−04:00 and ends at 02:30 with offset−05:00. Those are 04:30 and 07:30 UTC, giving three elapsed hours. Subtracting the two visible local hour labels gives only two. The viewer records the three-hour interval and checks programme identity separately instead of concluding that an extra hour must be a replay.
A focused way to proceed
- Record the full dated start and end with their offsets.
- Convert both endpoints to UTC.
- Compare elapsed duration with the listed programme duration.
When to stop or ask for help
Escalate only a remaining duration mismatch, carrying both original endpoints and their UTC equivalents.