FullCalendar does not reliably convert named timezone events without
a timezone adapter plugin. Instead, we pre-convert UTC datetimes to
the user's display timezone using isoToLocalDateTime and pass them to
FullCalendar with timeZone:'UTC', which displays wall-clock values as-is.
Drag/drop handlers now use delta-based UTC calculation from extendedProps
to send correct UTC times to the API regardless of display timezone.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
1a5b2f0e5e