adbDBGrid and edDateEdit null value

By code I set an editor for a column in this way,..
 Else If (dbgListini.Columns[ACol].FieldName = 'DTIN') or
    (dbgListini.Columns[ACol].FieldName = 'DTEN') then
    AEditor := edDateEdit;

The problem is that when the cell gain focus the dropdown calendar correctly is showed. and even if  i do not click any value the cell value is set to now.. This may be ok but the problem is that i can not clear the cell value setting to null.
How can achieve this?

When the inplace editor is set to edDateEdit, it is the Microsoft Windows standard datepicker control that is used as inplace editor and this editor doesn't have the capability to enter a blank value. If you want to enter a blank value, I'd suggest to use the TPlannerDatePicker control as inplace editor with the techniques as demonstrated in samples 24 or 55 of TAdvStringGrid.