get_posts creating 3 loops instead of 1

I’m trying to create an archive page that shows past posts from a certain category, sorted by month. This code works but the page appears to be running the loop 3 times instead of 1. See link

<?php
// Declare some helper vars
$previous_year = $year = 0;
$previous_month = $month = 0;
$ul_open = false;
// Get the posts
$myposts = get_posts('cat=16&numberposts=-1&orderby=post_date&order=DESC');
?>

<?php foreach($myposts as $post) : ?>	

	<?php

	// Setup the post variables
	setup_postdata($post);

	$year = mysql2date('Y', $post->post_date);
	$month = mysql2date('n', $post->post_date);
	$day = mysql2date('j', $post->post_date);

	?>

	<?php if($year != $previous_year || $month != $previous_month) : ?>

		<?php if($ul_open == true) : ?>
		</ul>
		<?php endif; ?>

		<h3><?php the_time('F Y'); ?></h3>

		<ul class="newslist">

		<?php $ul_open = true; ?>

	<?php endif; ?>

	<?php $previous_year = $year; $previous_month = $month; ?>

	<li class="<?php echo c2c_get_custom('Link Type'); ?>" style="list-style-type:none"><a href="<?php echo c2c_get_custom('URL'); ?>"><?php the_title(); ?></a></li>

<?php endforeach; ?>
	</ul>

I’ve tried resetting the loop before and after this piece of code with no luck. Any suggestions would be much appreciated!