dunno.php

<?php

$date1 = new DateTime('Mon, 15 Aug 05 15:52:01 +0000');
$date2 = new DateTime('Mon, 15 Aug 05 09:52:01 +0000');
$date3 = new DateTime('Mon, 15 Aug 05 10:32:01 +0000');
$paraSerOrdenado = [
    'array1' => [
        'datareal' => $date1,
        'datastr' => $date1->getTimestamp(), //timestamp é int
    ],
    'array2' => [
        'datareal' => $date2,
        'datastr' => $date2->getTimestamp(),
    ],
    'array3' => [
        'datareal' => $date3,
        'datastr' => $date3->getTimestamp(),
    ]
];

uasort($paraSerOrdenado, function($a, $b) {
    return (strcmp($a['datastr'], $b['datastr']));
});

var_dump($paraSerOrdenado);