Output the 'last updated' date in relative terms

functions.php

<?php
// Paste the code BELOW this line into your child theme functions.

/**
 * Output the 'last updated' date in relative terms
 * 
 * @author Reasons to Use Genesis
 * @link http://reasonstousegenesis.com/last-updated-date/
 */
add_filter( 'genesis_post_info', 'rtug_last_updated_date_relative' );
function rtug_last_updated_date_relative() {
	return 'Last updated [post_modified_date format="relative"]';
}