public function SetLastModified($LastModifiedDate) {
      $GMD = gmdate('D, d M Y H:i:s', $LastModifiedDate) . ' GMT';
      $this->SetHeader('Etag', '"'.$GMD.'"');
      $this->SetHeader('Last-Modified', $GMD);
      $IncomingHeaders = getallheaders();
      if (
         isset($IncomingHeaders['If-Modified-Since'])
         && isset ($IncomingHeaders['If-None-Match'])
      ) {
         $IfNoneMatch = $IncomingHeaders['If-None-Match'];
         $IfModifiedSince = $IncomingHeaders['If-Modified-Since'];
         if($GMD == $IfNoneMatch && $IfModifiedSince == $GMD) {
            $Database = Gdn::Database();
            if(!is_null($Database))
               $Database->CloseConnection();

            $this->SetHeader('Content-Length', '0');
            $this->SendHeaders();
            header('HTTP/1.1 304 Not Modified');
            exit("\n\n"); // Send two linefeeds so that the client knows the response is complete
         }
      }
   }