Index: wp-includes/general-template.php
===================================================================
--- wp-includes/general-template.php	(revision 4904)
+++ wp-includes/general-template.php	(working copy)
@@ -484,7 +484,7 @@
 			ORDER	BY post_date ASC
 			LIMIT 1");
 
-	echo '<table id="wp-calendar">
+	echo '<table id="wp-calendar" summary="' . __('Calendar') . '>
 	<caption>' . $wp_locale->get_month($thismonth) . ' ' . date('Y', $unixmonth) . '</caption>
 	<thead>
 	<tr>';