http://codex.wordpress.org/Function_Reference/the_date
When there are multiple posts on a page published under the SAME DAY, the_date() only displays the date for the first post (that is, the first instance of the_date()). To repeat the date for posts published under the same day, you should use the Template Tag the_time() or get_the_date() (since 3.0) with a date-specific format string.
Use to add the date set in the admin interface.
What you want is this:
$new_content .= "<strong>".$pr_meta['location'][0]." (".get_the_date($pr_date_format).") -</strong> ";