code: public function convertToUTC($timestamp, $timezone, $format = 'Y-m-d H:i:s')
      {
      	$date = new DateTime($timestamp, new DateTimeZone($timezone));
  
          $date->setTimezone(new DateTimeZone('UTC'));
  
          return $date->format($format);
      }
docs: @param integer $timestamp
  @param string $timezone
  @param string $format
  
  @return string