protected function getMonths()
    {
        $intSecondsPerMonth = ($this->isPositive()) ? DateTimeSpan::SECONDS_PER_MONTH : ((-1) * DateTimeSpan::SECONDS_PER_MONTH);
        $intMonths = floor($this->intSeconds / $intSecondsPerMonth);
        if ($this->isNegative()) {
            $intMonths = (-1) * $intMonths;
        }
        return $intMonths;
    }