how to exclude current year (2014) in archive.php ?

Hello everyone,
I use the code from this wordpress forum link.
It populate all post in years. Great! But I need to exclude the current year (it means from 2013 to oldest).

Need an advance,
thanks.
Milo

the code from the link are these:
in functions.php:

function posts_by_year() {
  // array to use for results
  $years = array();

  // get posts from WP
  $posts = get_posts(array(
    'numberposts' => -1,
    'orderby' => 'post_date',
    'order' => 'ASC',
    'post_type' => 'post',
    'post_status' => 'publish'
  ));

  // loop through posts, populating $years arrays
  foreach($posts as $post) {
    $years[date('Y', strtotime($post->post_date))][] = $post;
  }

  // reverse sort by year
  krsort($years);

  return $years;
}

in template:

<?php foreach(posts_by_year() as $year => $posts) : ?>
  <h2><?php echo $year; ?></h2>

  <ul>
    <?php foreach($posts as $post) : setup_postdata($post); ?>
      <li>
        <a href="<?php the_permalink(); ?>"><?php the_title(); ?></a>
      </li>
    <?php endforeach; ?>
  </ul>
<?php endforeach; ?>

thanks