c8bcc26e

By: Tom Sydney Kerckhove <syd@cs-syd.eu>

ical-recurrence: test that an instance in a daylight saving time gap is ignored

The TODO in ICal.Recurrence quotes this requirement but it is not
implemented.

On the 27th of March 2022 the local time in Zurich jumps from 02:00 to
03:00, so 02:30 does not exist on that day and a daily 02:30 event has
no instance there.  One is produced anyway, and resolveLocalTime then
maps it to 00:30Z, which unresolves to 01:30 local: an hour that
appears nowhere in the calendar.

The ambiguous direction, where a local time occurs twice at the end of
daylight saving time, happens to behave sensibly already by picking the
earlier offset.

Timeline