diff -r 7c48bb929e6e Lib/datetime.py
--- a/Lib/datetime.py	Tue Mar 27 11:49:21 2012 +0200
+++ b/Lib/datetime.py	Wed Mar 28 12:18:37 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 date 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")
+        date = cls(year, 1, 1)
+        if date.isocalendar()[1] != 1:
+            if date.weekday() > 3: #  Jan 1 is not in week one
+                date += timedelta(7 - date.weekday())
+        date += timedelta(7 * (week - 1))
+        if date.isocalendar()[0] != year:
+            raise ValueError("'week' within range but overflows to next year")
+        return date +timedelta(day - 1)
+
     # Pickle support.
 
     def _getstate(self):