The agenda window starts at the anchor's local midnight, which east of UTC
is the previous day's 22:00 UTC. All-day events live at UTC midnights with an
exclusive next-midnight end, so yesterday's all-day event (a birthday, say)
still overlaps today's window start and is returned by the provider.
groupAgendaDays then clamped its first day up to the anchor and, via a trailing
coerceAtLeast(firstDay) on the last day, pulled it onto the anchor's "today"
section — the multi-day fix only stopped the forward leak on interior days.
Drop instances whose true last day (resolved in UTC for all-day events) falls
before the anchor, or whose first day falls past the window end: they occupy no
visible day and must not be clamped onto an edge. Adds eastern-zone regression
tests for both edges.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Jean-Luc Makiola
4148196a36