Add the date of the order after the ID
Well, since you already loaded the order, I guess you could do:

&lt;div class="order-id"&gt;
  &lt;?php print render($content['order_id']); ?&gt;
  &lt;?php print format_date($order-&gt;created, 'custom', 'd-m-Y'); ?&gt;
&lt;/div&gt;