Index: wp-includes/feed-rss2.php
===================================================================
--- wp-includes/feed-rss2.php	(revision 5667)
+++ wp-includes/feed-rss2.php	(working copy)
@@ -10,6 +10,7 @@
 	xmlns:content="http://purl.org/rss/1.0/modules/content/"
 	xmlns:wfw="http://wellformedweb.org/CommentAPI/"
 	xmlns:dc="http://purl.org/dc/elements/1.1/"
+	xmlns:sy="http://purl.org/rss/1.0/modules/syndication/"
 	<?php do_action('rss2_ns'); ?>
 >
 
@@ -20,6 +21,8 @@
 	<pubDate><?php echo mysql2date('D, d M Y H:i:s +0000', get_lastpostmodified('GMT'), false); ?></pubDate>
 	<generator>http://wordpress.org/?v=<?php bloginfo_rss('version'); ?></generator>
 	<language><?php echo get_option('rss_language'); ?></language>
+	<sy:updatePeriod><?php echo apply_filters( 'rss_update_period', 'hourly' ); ?></sy:updatePeriod>
+	<sy:updateFrequency><?php echo apply_filters( 'rss_update_frequency', '1' ); ?></sy:updateFrequency>
 	<?php do_action('rss2_head'); ?>
 	<?php while( have_posts()) : the_post(); ?>
 	<item>
Index: wp-includes/feed-rss2-comments.php
===================================================================
--- wp-includes/feed-rss2-comments.php	(revision 5667)
+++ wp-includes/feed-rss2-comments.php	(working copy)
@@ -5,7 +5,9 @@
 ?>
 <!-- generator="wordpress/<?php echo $wp_version ?>" -->
 <rss version="2.0" 
-	xmlns:content="http://purl.org/rss/1.0/modules/content/">
+	xmlns:content="http://purl.org/rss/1.0/modules/content/"
+	xmlns:sy="http://purl.org/rss/1.0/modules/syndication/"
+>
 <channel>
 	<title><?php
 		if ( is_singular() )
@@ -19,7 +21,8 @@
 	<description><?php bloginfo_rss("description") ?></description>
 	<pubDate><?php echo gmdate('r'); ?></pubDate>
 	<generator>http://wordpress.org/?v=<?php echo $wp_version ?></generator>
-
+	<sy:updatePeriod><?php echo apply_filters( 'rss_update_period', 'hourly' ); ?></sy:updatePeriod>
+	<sy:updateFrequency><?php echo apply_filters( 'rss_update_frequency', '1' ); ?></sy:updateFrequency>
 <?php 
 if ( have_comments() ) : while ( have_comments() ) : the_comment();
 	$comment_post = get_post($comment->comment_post_ID);