You can set an "QItemDelegate" for a QTableWidget. Unfortunately, the GUI delegates are subclasses of QStyledItemDelegate. Both QItemDelegate and QStyledItemDelegate inherit from QAbstractItemDelegate, and they both seem to have the same API.
First thing I would try is to set the delegate for the date column to an instance of CcDateDelegate using setItemDelegate, and then see what happens.
Making a model would imply also making a view. I don't see any way to get one's hands on the view in QTableWidget, and it is the view that sets the delegate.