I changed the default setting to
dp.eventEndSpec = "Date";
This way I do not need to manually add one day to the end date anymore. This seems to work fine.
But if I want to display areas within this event. For each area I define start and end date, but I still habe to add one day to each area's end date. If I, e.g., have a "one-day-area", where start and end date are the same I need to "virtually" add one day to end to have it displayed correctly.
Is this intended or a bug?