The last day of a repeated event with no scheduled time (e. g. all-day-events) is not visilble e. g. in the month-view.
Reason: The correct end-date of the event is stored in the database but becomes converted into an Unix-timestamp with a time of 00:00:00. In functions.php/get_all_dates a $cdate with a time of 12:00:00 ist compared against this $until (as in $cdate <= $realend) and hence doesn't match the last day.
Fix: When creating an until-timestamp from the end-date in the database, set the time to 23:59:59. The get*Time* methods of the class RepeatingEvent might need some adjustment, too.