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<?php $data = [ [ "id" => "3f57dc7c-a698-e911-a95e-000d3a454330", "date" => [ [ "start_date" => "23.11.2020 07:00", "end_date" => "04.12.2020 16:00" ], [ "start_date" => "02.03.2020 07:00", "end_date" => "13.03.2020 16:00" ], [ "start_date" => "06.01.2020 07:00", "end_date" => "14.02.2020 21:00" ], [ "start_date" => "20.01.2020 07:00", "end_date" => "28.02.2020 07:00" ], [ "start_date" => "23.03.2020 07:00", "end_date" => "03.04.2020 15:00" ], [ "start_date" => "31.08.2020 06:00", "end_date" => "09.10.2020 15:00" ], [ "start_date" => "12.10.2020 06:00", "end_date" => "23.10.2020 15:00" ] ] ] ]; foreach ($data as $entry) { $tmp[] = usort($entry['date'], function($a, $b) { $a = DateTime::createFromFormat('d.m.Y H:i', $a['start_date']); $b = DateTime::createFromFormat('d.m.Y H:i', $b['start_date']); /* if ($a == $b) { return 0; } return $a < $b ? -1 : 1;*/ return $a <=> $b; }); } var_dump($data[0]['date']);