* If an incidence starts and also ends or is due at 00:00 of a day, the
   month view displayed it as a thin rectangle on the border between days.
 * Events that begin and end at 00:00 of the same day were displayed in
   the agenda across the whole day, as if they had 24-hour duration.
 * One-day events starting after 23:52:30 and ending at or before midnight
   were displayed below the bottom of the agenda.