private function getJ2000Day(\DateTime $dateTime)
    {
        $day = (integer) $dateTime->format('j');
        $month = (integer) $dateTime->format('n');
        $year = (integer) $dateTime->format('Y');
        return floor(367 * $year - (7 * ($year + (($month + 9) / 12))) / 4 + (275 * $month) / 9 + $day - 730530);
    }