Converting a timestamp to PHP date format for a field in a node template
As already pointed out by  Mohammed Shameem:

&lt;?php print gmdate("m-d-Y", $node-&gt;field_event_image['und'][0]['timestamp']) ?&gt;


However, the Drupal way would be:

&lt;?php print format_date($node-&gt;field_event_image['und'][0]['timestamp'], 'short'); ?&gt;


The latter construct will render the date in the standard short date format set up for the site.  The former will use the format you pick.  The Drupal way ensures that the date format is standardized throughout the site.