protected function yearSort($a, $b)
    {
        $aDates = $this->extractNewestDates($a);
        $bDates = $this->extractNewestDates($b);

        if (count($aDates) > 0 && count($bDates) > 0) {
            return $bDates[0] - $aDates[0];
        } elseif (count($aDates) > 0 && count($bDates) === 0) {
            return -1;
        } elseif (count($aDates) === 0 && count($bDates) > 0) {
            return 1;
        } else {
            return 0;
        }
    }