Distinguish the two occurrences
Python zoneinfo documents the fold flag for ambiguous times. Assigning a zone by itself does not prove a local time exists. This example uses the documented 2020 Los Angeles fall-back transition; the year and zone are deliberately fixed.
| Local input | Selected offset | UTC instant |
|---|---|---|
| 2020-11-01 01:00, America/Los_Angeles | First occurrence: -07:00 | 2020-11-01T08:00:00Z |
| Same local clock time | Second occurrence: -08:00 | 2020-11-01T09:00:00Z |
| No offset/occurrence selected | Unresolved | Do not silently choose |
Round-trip the chosen instant
For future appointments keep the intended local date/time and named zone as well as the resolved instant. Check transition cases with a timezone-aware library and its current data. A local time in a spring-forward gap needs a correction choice, not a guessed automatic shift.
Two systems exchange only “01:00” on this date. Can they agree on the instant?
Show the worked answer
No. Include the date, zone and selected offset/occurrence. The two valid occurrences in this example are one hour apart.