I am using a GridView with a CellEditTemplate to display a DatePicker with the date selection mode set to "Month". However this then meant that the CellValidation's event argument e.NewValue didn't contain the value selected by the user; rather it contained a minimum date value (#12:00:00am#).
After sifting through numerous articles searching for a resolution to this problem - the majority in this forum which referred to creating custom validation procedures and deriving new column types and another explaining the Validation Lifecycle that gave absolutely no information on cell validating using editing templates (and none that gave any examples) - I finally came across this article http://www.telerik.com/forums/custom-template-in-grid
that explained you simply had to use "e.EditingElement" to gain access to the editor used in the cell.
I am raising this thread in the hope that other users will be able to quickly locate the solution to this problem and not waste hours of their time.