public function Tags()
 {
     $select = array('Title');
     $query = new SQLQuery($select, 'PostTag');
     $query->selectField('count(PostTag.ID)', 'Number');
     $query->selectField('PostTag.ID');
     $query->addInnerjoin('MicroPost_Tags', 'PostTag.ID = MicroPost_Tags.PostTagID');
     $date = date('Y-m-d H:i:s', strtotime('-1 month'));
     $query->addWhere("MicroPost_Tags.Tagged > '{$date}'");
     $query->addWhere('"PostTag"."Title" NOT LIKE \'SELF_TAG%\'');
     $query->addGroupBy('PostTag.ID');
     $query->setLimit(20);
     $rows = $query->execute();
     $tags = ArrayList::create();
     foreach ($rows as $row) {
         $data = new ArrayData($row);
         $data->Link = Controller::join_links(TimelineController::URL_SEGMENT, '?tags=' . urlencode($data->Title));
         $tags->push($data);
     }
     return $tags;
 }