I see, I always forget that you cant use an aliased column in the WHERE clause.
After running the Data Assist Search wizard, you would need to edit the comparison code to add the date format
for example, the comparison may look like this:
$WADbSearch1->addComparisonFromEdit("DateColumn")","dateField","AND","=",0);
you would add the date format option like this:
$WADbSearch1->addComparisonFromEdit("DATE_FORMAT(DateColumn,\"%Y-%m-%d\")","dateField","AND","=",0);