//display a message on older posts
function so_older_post_message () {
$posted = get_the_time('U');
$current = current_time('timestamp');
//Convert difference in seconds to days
$diffTime = ($current - $posted) / (60*60*24);
if($diffTime > 365) {
echo '<div class=older-post-message>' . __('This post was written more than a year ago and <em>might</em> not be entirely accurate anymore.', 'wptips') . '</div><br />';
}
}
add_action('get_template_part_content','so_older_post_message');