This is because the MonthDay format is not supported in the DateEditor (which is a WinDatePicker underneath).
To accomplish this, you either need to wrap a date editor that supports this format around the CellEditorManager class, or you need to handle the GettingControlValue event on the CellEditorManager, so you can take the date value from the editor and change it so it fits the format you want when it displays in the grid. Note however that this second solution means that when editing the date, the year will also be displayed.
Imported from legacy forums. Posted by André (had 3003 views)