function publish_later_on_feed($where) {
    global $wpdb;
 
    if(is_feed()) {
	// timestamp in WP-format
	$now = gmdate('Y-m-d H:i:s');
 
	// value for wait; + device
	$wait = '5'; // integer
 
	// http://dev.mysql.com/doc/refman/5.0/en/date-and-time-functions.html#function_timestampdiff
	$device = 'MINUTE'; //MINUTE, HOUR, DAY, WEEK, MONTH, YEAR
 
	// add SQL-sytax to default $where
	$where .= " AND TIMESTAMPDIFF($device, $wpdb->posts.post_date_gmt, '$now') > $wait ";
    }
 
    return $where;
}
 
add_filter('posts_where', 'publish_later_on_feed');