As I know, all day event is sorted out alphabetically by default, despite
of the type of the occurrence
I set the view to "Day", and create a test all day event (Single
occurrence) with "a" as the subject. The "a" event will appear in the top
of the all day events; and if I changed the subject to "z", the test event
will move to the bottom of the all day events
If I've misunderstood the question, please feel free to correct me