Modified for use on my LUG's wiki, these are the changes I had to make to get 'pubDate' elements from Google Groups to format correctly

RSS-date-fix.patch

diff -ur RSS.orig/RSS.php RSS/RSS.php
--- RSS.orig/RSS.php	2010-10-26 21:16:18.000000000 -0500
+++ RSS/RSS.php	2010-10-27 00:21:22.000000000 -0500
@@ -199,8 +199,13 @@
 			$title = htmlspecialchars( trim( iconv( $charset, $wgOutputEncoding, $item['title'] ) ) );
 
 			if ( $date ) {
-				$pubdate = trim( iconv( $charset, $wgOutputEncoding, $item['pubdate'] ) );
-				$pubdate = date( $date, strtotime( $pubdate ) );
+				if ( isset( $item['date_timestamp'] ) ) {
+					$pubdate = $item['date_timestamp'];
+				} else {
+					$pubdate = trim( iconv( $charset, $wgOutputEncoding, $item['pubdate'] ) );
+					$pubdate = strtotime( $pubdate );
+				}
+				$pubdate = date( $date, $pubdate );
 			}
 
 			$d_title = wfRssFilter( $title, $rssFilter );
@@ -250,11 +255,21 @@
 			$d_title = wfRssFilter( $title, $rssFilter ) && wfRssFilterout( $title, $rssFilterout );
 			$title = wfRssHighlight( $title, $rssHighlight );
 			if ( $date ) {
-				$pubdate = isset( $item['pubdate'] ) ? trim( iconv( $charset, $wgOutputEncoding, $item['pubdate'] ) ) : '';
-				if ( $pubdate == '' ) {
-					$pubdate = trim( iconv( $charset, $wgOutputEncoding, $item['dc']['date'] ) );
+				if ( isset( $item['date_timestamp'] ) ) {
+					$pubdate = $item['date_timestamp'];
+				} else {
+					if ( $pubdate == '' ) {
+						$pubdate = isset( $item['pubdate'] ) ? trim( iconv( $charset, $wgOutputEncoding, $item['pubdate'] ) ) : '';
+					}
+					if ( $pubdate == '' ) {
+						$pubdate = isset( $item['updated'] ) ? trim( iconv( $charset, $wgOutputEncoding, $item['updated'] ) ) : '';
+					}
+					if ( $pubdate == '' ) {
+						$pubdate = isset( $item['dc']['date'] ) ? trim( iconv( $charset, $wgOutputEncoding, $item['dc']['date'] ) ) : '';
+					}
+					$pubdate = strtotime( $pubdate );
 				}
-				$pubdate = date( $date, strtotime( $pubdate ) );
+				$pubdate = date( $date, $pubdate );
 			}
 
 			if ( $d_title && !in_array( $title, $displayed ) ) {
diff -ur RSS.orig/RSSParse.php RSS/RSSParse.php
--- RSS.orig/RSSParse.php	2010-10-26 21:16:18.000000000 -0500
+++ RSS/RSSParse.php	2010-10-27 00:06:53.000000000 -0500
@@ -339,6 +339,11 @@
 					if ( $epoch && $epoch > 0 ) {
 						$item['date_timestamp'] = $epoch;
 					}
+				} elseif ( isset( $item['updated'] ) ) {
+					$epoch = @strtotime( $item['updated'] );
+					if ( $epoch > 0 ) {
+						$item['date_timestamp'] = $epoch;
+					}
 				}
 
 				$this->items[$i] = $item;
@@ -360,7 +365,12 @@
 						$item['date_timestamp'] = $epoch;
 					}
 				} elseif ( isset( $item['pubdate'] ) ) {
-					$epoch = @strtotime( $item['pubdate'] );
+					$epoch = @strtotime( str_replace( 'UT', 'UTC', $item['pubdate'] ) );
+					if ( $epoch > 0 ) {
+						$item['date_timestamp'] = $epoch;
+					}
+				} elseif ( isset( $item['updated'] ) ) {
+					$epoch = @strtotime( $item['updated'] );
 					if ( $epoch > 0 ) {
 						$item['date_timestamp'] = $epoch;
 					}

Revised to format the dates in Atom 'updated' fields.