Index: Doc/lib/libdatetime.tex
===================================================================
--- Doc/lib/libdatetime.tex	(revision 54295)
+++ Doc/lib/libdatetime.tex	(working copy)
@@ -368,6 +368,10 @@
   \lineii{\var{date1} < \var{date2}}
    {\var{date1} is considered less than \var{date2} when \var{date1}
    precedes \var{date2} in time. (4)}
+   
+  \lineii{\var{datetime} in \var{date}}
+   {\var{datetime} occurs on \var{date}.  This is a shortcut for
+   \code{datetime.date() == date}. \versionadded{2.6}}
 
 \end{tableii}
 
Index: Lib/test/test_datetime.py
===================================================================
--- Lib/test/test_datetime.py	(revision 54295)
+++ Lib/test/test_datetime.py	(working copy)
@@ -945,6 +945,29 @@
             self.assertRaises(TypeError, lambda: badarg < t1)
             self.assertRaises(TypeError, lambda: badarg > t1)
             self.assertRaises(TypeError, lambda: badarg >= t1)
+            
+    def test_contains_datetime(self):
+        d = self.theclass(2, 3, 4)
+        
+        dt1 = datetime(2, 3, 4, 0, 0, 0)
+        self.failUnless(dt1 in d)
+        
+        dt2 = datetime(2, 3, 4, 5, 6, 7)
+        self.failUnless(dt2 in d)
+        
+        dt3 = datetime(2, 3, 5, 0, 0, 0)
+        self.failUnless(dt3 not in d)
+        
+        # These should all raise TypeErrors
+        for obj in [timedelta(), time(), date(2, 3, 4)]:
+            self.assertRaises(TypeError, d.__contains__, obj)
+            
+        # ...but subclasses of datetime are alright
+        class DT(datetime):
+            pass
+            
+        dts = DT(2, 3, 4, 0, 0, 1)
+        self.failUnless(dts in d)
 
     def test_mixed_compare(self):
         our = self.theclass(2000, 4, 5)
@@ -1375,6 +1398,13 @@
             self.failUnless(not t2 <= t1)
             self.assertEqual(cmp(t1, t2), -1)
             self.assertEqual(cmp(t2, t1), 1)
+            
+    def test_contains_datetime(self):
+        # Override this (inherited from TestDate); datetime
+        #  objects can't "contain" anything.
+    
+        dt = self.theclass(2003, 2, 7, 16, 48, 37)
+        self.assertRaises(TypeError, dt.__contains__, dt)
 
 
     # A helper for timestamp constructor tests.
Index: Modules/datetimemodule.c
===================================================================
--- Modules/datetimemodule.c	(revision 54295)
+++ Modules/datetimemodule.c	(working copy)
@@ -2529,6 +2529,19 @@
 	return diff_to_bool(diff, op);
 }
 
+static int
+date_contains(PyDateTime_Date *self, PyObject *other)
+{
+    if (!PyDateTime_Check(other)) {
+        PyErr_SetString(PyExc_TypeError, "dates can only contain datetimes");
+        return -1;
+    }
+    
+    return GET_YEAR(self)  == GET_YEAR(other) &&
+           GET_MONTH(self) == GET_MONTH(other) &&
+           GET_DAY(self)   == GET_DAY(other);
+}
+
 static PyObject *
 date_timetuple(PyDateTime_Date *self)
 {
@@ -2680,6 +2693,19 @@
 	0,						/* nb_nonzero */
 };
 
+static PySequenceMethods date_as_sequence = {
+	0,			/* sq_length */
+	0,		/* sq_concat */
+	0,		/* sq_repeat */
+	0,		/* sq_item */
+	0,		/* sq_slice */
+	0,		/* sq_ass_item */
+	0,	/* sq_ass_slice */
+	(objobjproc)date_contains,		/* sq_contains */
+	0,	/* sq_inplace_concat */
+	0,	/* sq_inplace_repeat */
+};
+
 static PyTypeObject PyDateTime_DateType = {
 	PyObject_HEAD_INIT(NULL)
 	0,						/* ob_size */
@@ -2693,7 +2719,7 @@
 	0,						/* tp_compare */
 	(reprfunc)date_repr,				/* tp_repr */
 	&date_as_number,				/* tp_as_number */
-	0,						/* tp_as_sequence */
+	&date_as_sequence,   			/* tp_as_sequence */
 	0,						/* tp_as_mapping */
 	(hashfunc)date_hash,				/* tp_hash */
 	0,              				/* tp_call */
@@ -4204,6 +4230,15 @@
 	return NULL;
 }
 
+static int
+datetime_contains(PyDateTime_DateTime *self, PyObject *other)
+{
+    PyErr_Format(PyExc_TypeError,
+		     "argument of type '%.200s' is not iterable",
+		     self->ob_type->tp_name);
+    return -1;
+}
+
 static long
 datetime_hash(PyDateTime_DateTime *self)
 {
@@ -4558,6 +4593,20 @@
 	0,					/* nb_nonzero */
 };
 
+/* Don't want to inherit sq_contains from date */
+static PySequenceMethods datetime_as_sequence = {
+	0,			/* sq_length */
+	0,		/* sq_concat */
+	0,		/* sq_repeat */
+	0,		/* sq_item */
+	0,		/* sq_slice */
+	0,		/* sq_ass_item */
+	0,	/* sq_ass_slice */
+	(objobjproc)datetime_contains,		/* sq_contains */
+	0,	/* sq_inplace_concat */
+	0,	/* sq_inplace_repeat */
+};
+
 statichere PyTypeObject PyDateTime_DateTimeType = {
 	PyObject_HEAD_INIT(NULL)
 	0,					/* ob_size */
@@ -4571,7 +4620,7 @@
 	0,					/* tp_compare */
 	(reprfunc)datetime_repr,		/* tp_repr */
 	&datetime_as_number,			/* tp_as_number */
-	0,					/* tp_as_sequence */
+	&datetime_as_sequence,	    	/* tp_as_sequence */
 	0,					/* tp_as_mapping */
 	(hashfunc)datetime_hash,		/* tp_hash */
 	0,              			/* tp_call */