Validate date type with era

I would like to validate a date field with era using rules in my model. I looked at the CDateFormater->format() method and I find some explanations of the pattern. So I try this:

public function rules() {

        return array(

           array('dc_date_issued', 'type', 'type' => 'date', 'message' => '{attribute}: is not a valid date!', 

                 'dateFormat' => 'yyyy-MM-dd G'),



But this seems not to work. The rule check rejects my date entries like ‘2001-11-30 AD’ or ‘0200-12-29 BC’. I have tried different patterns like yyyy-MM-dd GG or yyyy-MM-dd GGG. Same problem…

Any idea?

Thanks for your answer in advance

– Franck