Get Unique years from post type

wp-get-unique-year-from-post-type.php

<?php
  /**
   * Get posts year
   * @return [type] [description]
   */
  function get_post_years() {
    global $wpdb;
    $sql = "SELECT YEAR(STR_TO_DATE(p.post_date, '%Y')) as year
            FROM $wpdb->posts as p
            WHERE p.post_type = 'post' AND p.post_status = 'publish'
            GROUP BY year
            ORDER BY year DESC";
    return $wpdb->get_col($sql);
  }

?>

<?php
  // Templates
  $years = get_post_years();
  if (count($years)) : ?>
    <ul>
      <?php foreach ( $years as $year ): ?>
        <li><a href="<?php echo home_url('/') . $year; ?> " title=""><?php print $year; ?></a></li>
      <?php endforeach ?>
    </ul>
<?php endif; ?>