WordPress: Set metatag to no index for older posts

wp-add-noindex-to-older-posts.php

<?php
// WordPress: set no index for older posts in WordPress
// -----------------------------

// check the post age
// returns true if older than...

function hhdev_is_old_post($days = 730) {
	// 2 years old = 730
	
	$days = (int) $days;
	$offset = $days*60*60*24;
	
	if ( get_post_time() < date('U') - $offset ) return true;
	
	return false;
}

// add Meta Tags in post when older than 2 years
function hhdev_add_age_meta_tags() {

	if( is_single() && hhdev_is_old_post() ) echo '<meta name="robots" content="noindex,follow" />';
}

add_action('wp_head', 'hhdev_add_age_meta_tags');