--- CODE/Drupal/calendar/archive/archive.module.orig	2009-02-01 22:47:28.000000000 +0200
+++ CODE/Drupal/calendar/archive/archive.module	2009-02-01 22:51:31.000000000 +0200
@@ -127,7 +127,10 @@ function theme_archive_block_calendar($t
 	// Grab the first day of the month using the user's timezone
 	list($start_year, $start_month) = explode(' ', format_date($timestamp, 'custom', 'Y m'));
 	$start = gmmktime( 0, 0, 0, (int)$start_month, 1, (int)$start_year);
-	$weekday = gmdate('w', $start) - $first_day_of_week;
+        $weekday = gmdate('w', $start);
+        if( $first_day_of_week ) {
+          $weekday = ($weekday?$weekday:7) - $first_day_of_week;
+        }
 	$days_row = array();
 
 	// From http://www.theadminzone.com/forums/showthread.php?t=17490