The previous commit asserted southern zones round-trip through iCal unchanged
but verified it only by reasoning. Close that gap with explicit tests:
- A Sydney VTIMEZONE export block: TZID:Australia/Sydney, DAYLIGHT->+1100
(AEDT) / STANDARD->+1000 (AEST), first-Sunday rules (BYMONTH=10/4 BYDAY=1SU),
and DAYLIGHT DTSTART:19701004T020000 — confirming the -480 rule time folds
the from-offset back to the correct local 02:00 AEST transition.
- A southern-zone DTSTART;TZID export -> import round-trip preserving :dtstart.
+7 ical tests (now 63).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
giles
6716af69dc