Zend FR

        $date = new Zend_Date;
        $date->setOptions(array('fix_dst' => false));

        $calendrier = array();

        $periode = $this->_getParam('periode');

        if (strlen($periode)) {
            list($annee, $mois) = explode('-', $periode);
            $date->set((int) $annee . '-' . (int) $mois . '-01 00:00:00');
            $nb_jours = $date->get('ddd');
        } else {
            list($annee, $mois) = explode('-', $date->get('YYYY-MM'));
            $nb_jours = $date->get('ddd');
        }