When the all-day checkbox is ticked, transforming to the
UTC timezone may change the dates of the event. On positive
timezone offsets, this happens frequently.
Fix that by only transforming to a timezone when the event
is not marked as all-day.
Fixes https://gitlab.gnome.org/GNOME/gnome-calendar/issues/338
The view knows its time range, and knows what the
next or previous dates should be. So instead of
calculating the next date manually, ask the views
for that.
Florian Latifi