Convert Custom Date with PHP

datetime.php

<?php
$depart = "140117";
$arrive = "arriving on 21 January 2017";

$dep_date = DateTime::createFromFormat('dmy', $depart);
$arr_date = DateTime::createFromFormat('\a\r\r\i\v\i\n\g \o\n d F Y', $arrive);

$date_diff = $dep_date->diff($arr_date);

$dep_date = $dep_date->format('d-m-Y');
$arr_date = $arr_date->format('m/d/Y');

echo "The difference between ". $dep_date ." and ". $arr_date ." is ". $date_diff->d ." days.";
?>