Sortering på dato med identiske keys

Hej,

Jeg trækker datoer ud fra to databaser (med fødselsdage og møder), disse kan falde på samme dato. Hvordan får jeg dem vist?

Følgende haves:

$this_year = date("Y");
$next_year = date('Y', strtotime('+1 year'));

$interval_date = date('Y-m-d', strtotime(date("Y-m-d"). ' +5 month'));

$qry_cal = "
SELECT birthday AS sorter, birthday, NULL AS date, first AS beskr FROM all_users
UNION ALL
SELECT date AS sorter, NULL AS birthday, date, description AS beskr FROM calender_".$this_year." WHERE date > CURDATE()
UNION ALL
SELECT date AS sorter, NULL AS birthday, date, description AS beskr FROM calender_".$next_year." WHERE date > CURDATE()
ORDER BY MONTH(sorter), DAY(sorter), YEAR(sorter) ASC";
$result_cal = mysqli_query($dbc, $qry_cal);

$date2 = array();
while ($row = mysqli_fetch_array($result_cal)) {
    if (!empty($row['birthday'])) {
        $now = time();
        $dob = strtotime($row['birthday']);
        $birthd = explode("-", $row['birthday']);
        $dob_thisyear = date("Y").'-'.$birthd[1].'-'.$birthd[2];
        $difference = $now - $dob;
        $age = floor($difference / 31556926)+1;
       
        $day = date("d-m-Y", strtotime($row['birthday']));
        if ($dob_thisyear >= date("Y-m-d")) {
            $dob_next = $dob_thisyear;
        } else {
            $year_next = date('Y', strtotime('+1 year'));
            $dob_next = $year_next.'-'.$birthd[1].'-'.$birthd[2];
        }
        if ($dob_next <= $interval_date) {
            $date2[$dob_next] = ' <img src="danneb.png" height="20" width="20">&nbsp;&nbsp;'.$row['beskr'].' '.($age).' år';
        }
    }
   
    if (!empty($row['date'])) {
        if ($row['date'] <= $interval_date) {
            $date2[$row['date']] = ' <img src="calendar.png" height="20" width="20">&nbsp;&nbsp;'.$row['beskr'];
        }
    }

}

ksort($date2);

foreach ($date2 as $d => $b) {
    echo $d.'-'.$b.'<br>';
}