Two correct clocks can move apart temporarily
A programme may continue at the same local hour in its home market while its start moves for an overseas viewer. That can happen because the source and destination locations change seasonal rules on different dates. Neither device has to be wrong.
A reminder stored as a complete date and source time zone can follow the change. A note that says add five hours cannot know which transition has already happened. The dated calculation is therefore the useful unit for a programme reminder.
Compare dates before, during and after the transition period
The following UTC instants are chosen to reveal the relationship represented in IANA 2026f. They are examples, not a fixture calendar.
| UTC example | America/New_York | Europe/London | Europe/Paris |
|---|---|---|---|
| 2027-02-15 20:00:00 UTC | 2027-02-15 15:00 (UTC-05:00) | 2027-02-15 20:00 (UTC+00:00) | 2027-02-15 21:00 (UTC+01:00) |
| 2027-03-20 20:00:00 UTC | 2027-03-20 16:00 (UTC-04:00) | 2027-03-20 20:00 (UTC+00:00) | 2027-03-20 21:00 (UTC+01:00) |
| 2027-04-10 20:00:00 UTC | 2027-04-10 16:00 (UTC-04:00) | 2027-04-10 21:00 (UTC+01:00) | 2027-04-10 22:00 (UTC+02:00) |
A recurring programme and a recurring instant differ
A series scheduled every week at a source-local hour does not necessarily occupy the same UTC hour all year. Conversely, an event explicitly scheduled in UTC keeps its instant while the local display changes. The announcement should make clear which type of schedule is being used.
When a guide seems correct most of the year but shifts near clock-change weeks, compare the source and destination rules before assuming the broadcaster changed its programme. A temporary seasonal relationship is a different issue from selecting the wrong regional edition.
Keep a reproducible comparison
Record the source date and time zone, the expected local result and the actual displayed guide time. One concrete programme example is enough to show a conversion discrepancy more clearly than changing every guide entry by hand.
Questions about this guide
Can both clocks be correct when a programme moves locally by an hour?
Yes. The seasonal relationship between the source and destination can change even if both devices apply their own rules correctly.
Are these dates a programme schedule?
No. They are selected UTC examples calculated from IANA 2026f.