<?php
// Put inside Post Loop

$time_defined_as_old = 60*60*24*365; // A Year

if((date('U')-get_the_time('U')) > $time_defined_as_old) {
  echo '<div class="notice"><strong>Notice</strong><br />This article is published more than one year ago. Information in this article might be irrelevant with current situation</div>';
}

?>

## Benefit
To notify visitors that the current post they are viewing is an old post. Suitable for Blog / Website that provide timely articles

Notify of Old Post in WordPress

php, wordpress

PHP