League\Period\Period::getDateInterval PHP Method

    public function getDateInterval()
    {
        return $this->startDate->diff($this->endDate);
    }

 /**
  * Returns the difference between two Period objects expressed in \DateInterval
  *
  * @param Period $period
  *
  * @return DateInterval
  */
 public function dateIntervalDiff(Period $period)
 {
     return $this->endDate->diff($this->withDuration($period->getDateInterval())->endDate);
 }