Source

File: wp-includes/deprecated.php

function get_boundary_post_rel_link($title = '%title', $in_same_cat = false, $excluded_categories = '', $start = true) {
	_deprecated_function( __FUNCTION__, '3.3.0' );

	$posts = get_boundary_post($in_same_cat, $excluded_categories, $start);
	// If there is no post, stop.
	if ( empty($posts) )
		return;

	// Even though we limited get_posts() to return only 1 item it still returns an array of objects.
	$post = $posts[0];

	if ( empty($post->post_title) )
		$post->post_title = $start ? __('First Post') : __('Last Post');

	$date = mysql2date(get_option('date_format'), $post->post_date);

	$title = str_replace('%title', $post->post_title, $title);
	$title = str_replace('%date', $date, $title);
	$title = apply_filters('the_title', $title, $post->ID);

	$link = $start ? "<link rel='start' title='" : "<link rel='end' title='";
	$link .= esc_attr($title);
	$link .= "' href='" . get_permalink($post) . "' />\n";

	$boundary = $start ? 'start' : 'end';
	return apply_filters( "{$boundary}_post_rel_link", $link );
}