public function getDifferenceInMonths($compare = null)
        {
            if (!$compare) {
                $compare = new Date(null, $this->getTimezone());
            }

            $difference = $this->diff($compare);

            list($years, $months) = explode(':', $difference->format('%y:%m'), 2);

            return (($years * 12) + $months) * $difference->format('%r1');
        }