This property is obsolete.
When an editor's mask type is set to MaskType.DateTime or MaskType.DateTimeAdvancingCaret, a date editor prevents an end-user from entering an invalid date-time value. Only a valid date-time value that matches the pattern specified by the EditMask property can be entered.
When an editor's mask type is set to MaskType.None, the editor allows an end-user to enter any text (not only strings corresponding to date/time values). A date editor will make an attempt to convert the entered text to a date/time value. If the text cannot be converted the editor's edit value will be set to null. To implement a custom conversion algorithm handle the RepositoryItem.ParseEditValue event.