diff -r 5fb1057bd490 Lib/calendar.py
--- a/Lib/calendar.py	Sat Jul 21 21:23:00 2012 -0700
+++ b/Lib/calendar.py	Sun Jul 22 16:23:11 2012 +0200
@@ -161,7 +161,10 @@
         oneday = datetime.timedelta(days=1)
         while True:
             yield date
-            date += oneday
+            try:
+                date += oneday
+            except OverflowError:
+                break
             if date.month != month and date.weekday() == self.firstweekday:
                 break
 
diff -r 5fb1057bd490 Lib/test/test_calendar.py
--- a/Lib/test/test_calendar.py	Sat Jul 21 21:23:00 2012 -0700
+++ b/Lib/test/test_calendar.py	Sun Jul 22 16:23:11 2012 +0200
@@ -262,6 +262,10 @@
         new_october = calendar.TextCalendar().formatmonthname(2010, 10, 10)
         self.assertEquals(old_october, new_october)
 
+    def test_itermonthdates(self):
+        # ensure itermonthdates works for all months
+        list(calendar.Calendar().itermonthdates(9999, 12))
+
 
 class MonthCalendarTestCase(unittest.TestCase):
     def setUp(self):