protected function jdToY($julian_day)
    {
        // Estimate the year, and underestimate it, it will be refined after
        $year = max((int) ((($julian_day - 347998) * 98496) / 35975351) - 1, 1);

        // Adjust by adding years;
        while ($julian_day >= $this->yToJd($year + 1)) {
            $year++;
        }

        return $year;
    }