Zend FR

        $frenchDate = new Zend_Validate_Date('dd/MM/yyyy');
        $frenchDate->setMessages(array(Zend_Validate_Date::FALSEFORMAT  => 'Pas dans le bon format',Zend_Validate_Date::INVALID =>'date non valide'));
        
        //user_birthday
        $birthday = new Zend_Form_Element_Text('birthday');
        $birthday->setLabel('Date de Naissance')
        ->addValidator($frenchDate);
        //->addValidator(new Zend_Validate_Date());