diff -urN archive.orig/archive.module archive/archive.module
--- archive.orig/archive.module	2008-04-28 10:59:57.000000000 +0900
+++ archive/archive.module	2008-06-07 12:28:29.000000000 +0900
@@ -115,6 +115,7 @@
   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;
+  if (gmdate('w', $start) == 0 && $first_day_of_week != 0) $weekday += 7;
   $days_row = array();
   
   // From http://www.theadminzone.com/forums/showthread.php?t=17490