diff -r 7c48bb929e6e Doc/library/datetime.rst
--- a/Doc/library/datetime.rst	Tue Mar 27 11:49:21 2012 +0200
+++ b/Doc/library/datetime.rst	Sat Mar 31 05:10:44 2012 -0500
@@ -417,6 +417,15 @@
    d``.
 
 
+.. classmethod:: date.from_iso_week(year, week, day=1)
+
+    Return the date corresponding to the ISO year, week and optionally day.
+    :exc:`ValueError` is raised unless ``1 <= week <= 53``, ``1 <= day <= 7``, 
+    further :exc:`ValueError` is raised if the choosen week overflows the year.
+    The default behaviour, without supplying a day, returns the date for monday
+    of that week, if a ISO day is supplied that days date is returned.
+
+
 Class attributes:
 
 .. attribute:: date.min
diff -r 7c48bb929e6e Lib/datetime.py
--- a/Lib/datetime.py	Tue Mar 27 11:49:21 2012 +0200
+++ b/Lib/datetime.py	Sat Mar 31 05:10:44 2012 -0500
@@ -896,6 +896,23 @@
                 week = 0
         return year, week+1, day+1
 
+    @classmethod
+    def from_iso_week(cls, year, week, day=1):
+        """Construct a self from ISO year, week number and weekday (default 1)
+        """
+        if not 1 <= day <= 7:
+            raise ValueError("'day' invalid, acceptable range 1-7")
+        if not 1 <= week <= 53:
+            raise ValueError("'week' invalid, accaptable range 1-53")
+        self = cls(year, 1, 1)
+        if self.isocalendar()[1] != 1:
+            if self.weekday() > 3:  # Jan 1 is not in week one
+                self += timedelta(7 - self.weekday())
+        self += timedelta(7 * (week - 1))
+        if self.isocalendar()[0] != year:
+            raise OverflowError("'week' within range but overflows to next year")
+        return self + timedelta(day - 1)
+
     # Pickle support.
 
     def _getstate(self):
diff -r 7c48bb929e6e Lib/test/datetimetester.py
--- a/Lib/test/datetimetester.py	Tue Mar 27 11:49:21 2012 +0200
+++ b/Lib/test/datetimetester.py	Sat Mar 31 05:10:44 2012 -0500
@@ -980,6 +980,39 @@
             self.assertRaises(OverflowError, self.theclass.fromtimestamp,
                               insane)
 
+    def test_from_iso_week(self):
+        # This is an edge case, 1998 had 53 weeks
+        year, month, week, day = 1998, 12, 53, 31
+        d = self.theclass.from_iso_week(year, week)
+        self.assertEqual(d.year, year)
+        self.assertEqual(d.month, month)
+        self.assertEqual(d.day, day)
+
+    def test_from_iso_week_overflow(self):
+        # Test that we get the OverflowError when the year has 52 weeks
+        year, week = 1999, 53
+        self.assertRaises(OverflowError, self.theclass.from_iso_week, year,
+                          week)
+
+    def test_from_iso_week_value_week(self):
+        # Test that we get the ValueError when we try setting an invalid week
+        year, week = 1999, 54
+        self.assertRaises(ValueError, self.theclass.from_iso_week, year,
+                          week)
+        year, week = 1999, 0
+        self.assertRaises(ValueError, self.theclass.from_iso_week, year,
+                          week)
+
+    def test_from_iso_week_value_day(self):
+        # Test that we get the ValueError when we try setting an invalid week
+        year, week, day = 1999, 1, 0
+        self.assertRaises(ValueError, self.theclass.from_iso_week, year,
+                          week, day)
+        year, week, day = 1999, 1, 8
+        self.assertRaises(ValueError, self.theclass.from_iso_week, year,
+                          week, day)
+
+
     def test_today(self):
         import time