SELECT wposts.*,CONVERT(str_to_date(wpostmeta.meta_value,'%d/%m/%Y %H:%i:%s'),date) as mydate FROM wp_posts wposts LEFT JOIN wp_postmeta wpostmeta ON wposts.ID = wpostmeta.post_id WHERE ((wposts.post_type = 'colloque') OR (wposts.post_type = 'journee')) AND wpostmeta.meta_key = 'Date de début' AND wposts.post_status = 'publish' AND str_to_date(wpostmeta.meta_value,'%d/%m/%Y') > '2015-09-01' order by mydate desc ;