diff --git a/Doc/lib/libdatetime.tex b/Doc/lib/libdatetime.tex
index a7d9926..8bfc2bf 100644
--- a/Doc/lib/libdatetime.tex
+++ b/Doc/lib/libdatetime.tex
@@ -365,6 +365,12 @@
 
 Instance methods:
 
+  - replace(year=, month=, day=)
+    Return a date with the same value, except for those fields given
+    new values by whichever keyword arguments are specified.  For
+    example, if \code{d == date(2002, 12, 31)}, then
+    \code{d.replace(day=26) == date(2000, 12, 26)}.
+
   - timetuple()
     Return a 9-element tuple of the form returned by
     \function{time.localtime()}.  The hours, minutes and seconds are
@@ -591,6 +597,10 @@
   - time()
     Return time object with same hour, minute, second and microsecond.
 
+  - replace(year=, month=, day=, hour=, minute=, second=, microsecond=)
+    Return a datetime with the same value, except for those fields given
+    new values by whichever keyword arguments are specified.
+
   - timetuple()
     Return a 9-element tuple of the form returned by
     \function{time.localtime()}.
@@ -710,6 +720,10 @@
 
 Instance methods:
 
+  - replace(hour=, minute=, second=, microsecond=)
+    Return a time with the same value, except for those fields given
+    new values by whichever keyword arguments are specified.
+
   - isoformat()
     Return a string representing the time in ISO 8601 format,
         HH:MM:SS.mmmmmm
@@ -857,6 +871,12 @@
 
 Instance methods:
 
+  - replace(hour=, minute=, second=, microsecond=, tzinfo=)
+    Return a timetz with the same value, except for those fields given
+    new values by whichever keyword arguments are specified.  Note that
+    \code{tzinfo=None} can be specified to create a naive timetz from an
+    aware timetz.
+
   - isoformat()
     Return a string representing the time in ISO 8601 format,
         HH:MM:SS.mmmmmm
@@ -1048,11 +1068,18 @@
     Return \class{timetz} object with same hour, minute, second, microsecond,
     and tzinfo.
 
+  - replace(year=, month=, day=, hour=, minute=, second=, microsecond=,
+            tzinfo=)
+    Return a datetimetz with the same value, except for those fields given
+    new values by whichever keyword arguments are specified.  Note that
+    \code{tzinfo=None} can be specified to create a naive datetimetz from
+    an aware datetimetz.
+
   - utcoffset()
     If \member{tzinfo} is \code{None}, returns \code{None}, else
     \code{tzinfo.utcoffset(self)}.
 
-  - tzname():
+  - tzname()
     If \member{tzinfo} is \code{None}, returns \code{None}, else
     \code{tzinfo.tzname(self)}.
 
diff --git a/Lib/test/test_datetime.py b/Lib/test/test_datetime.py
index 6838e47..fe52212 100644
--- a/Lib/test/test_datetime.py
+++ b/Lib/test/test_datetime.py
@@ -874,6 +874,28 @@
         self.assertEqual(cls(1900, 1, 1).strftime("%Y"), "1900")
         for y in 1, 49, 51, 99, 100, 1000, 1899:
             self.assertRaises(ValueError, cls(y, 1, 1).strftime, "%Y")
+
+    def test_replace(self):
+        cls = self.theclass
+        args = [1, 2, 3]
+        base = cls(*args)
+        self.assertEqual(base, base.replace())
+
+        i = 0
+        for name, newval in (("year", 2),
+                             ("month", 3),
+                             ("day", 4)):
+            newargs = args[:]
+            newargs[i] = newval
+            expected = cls(*newargs)
+            got = base.replace(**{name: newval})
+            self.assertEqual(expected, got)
+            i += 1
+
+        # Out of bounds.
+        base = cls(2000, 2, 29)
+        self.assertRaises(ValueError, base.replace, year=2001)
+
 #############################################################################
 # datetime tests
 
@@ -1248,6 +1270,32 @@
         self.assertRaises(TypeError, combine, d, t, 1) # too many args
         self.assertRaises(TypeError, combine, "date", "time") # wrong types
 
+    def test_replace(self):
+        cls = self.theclass
+        args = [1, 2, 3, 4, 5, 6, 7]
+        base = cls(*args)
+        self.assertEqual(base, base.replace())
+
+        i = 0
+        for name, newval in (("year", 2),
+                             ("month", 3),
+                             ("day", 4),
+                             ("hour", 5),
+                             ("minute", 6),
+                             ("second", 7),
+                             ("microsecond", 8)):
+            newargs = args[:]
+            newargs[i] = newval
+            expected = cls(*newargs)
+            got = base.replace(**{name: newval})
+            self.assertEqual(expected, got)
+            i += 1
+
+        # Out of bounds.
+        base = cls(2000, 2, 29)
+        self.assertRaises(ValueError, base.replace, year=2001)
+
+
 class TestTime(unittest.TestCase):
 
     theclass = time
@@ -1464,6 +1512,31 @@
         self.failUnless(not cls(0))
         self.failUnless(not cls())
 
+    def test_replace(self):
+        cls = self.theclass
+        args = [1, 2, 3, 4]
+        base = cls(*args)
+        self.assertEqual(base, base.replace())
+
+        i = 0
+        for name, newval in (("hour", 5),
+                             ("minute", 6),
+                             ("second", 7),
+                             ("microsecond", 8)):
+            newargs = args[:]
+            newargs[i] = newval
+            expected = cls(*newargs)
+            got = base.replace(**{name: newval})
+            self.assertEqual(expected, got)
+            i += 1
+
+        # Out of bounds.
+        base = cls(1)
+        self.assertRaises(ValueError, base.replace, hour=24)
+        self.assertRaises(ValueError, base.replace, minute=-1)
+        self.assertRaises(ValueError, base.replace, second=100)
+        self.assertRaises(ValueError, base.replace, microsecond=1000000)
+
 # A mixin for classes with a tzinfo= argument.  Subclasses must define
 # theclass as a class atribute, and theclass(1, 1, 1, tzinfo=whatever)
 # must be legit (which is true for timetz and datetimetz).
@@ -1735,6 +1808,45 @@
         t = cls(0, tzinfo=FixedOffset(-24*60, ""))
         self.assertRaises(ValueError, lambda: bool(t))
 
+    def test_replace(self):
+        cls = self.theclass
+        z100 = FixedOffset(100, "+100")
+        zm200 = FixedOffset(timedelta(minutes=-200), "-200")
+        args = [1, 2, 3, 4, z100]
+        base = cls(*args)
+        self.assertEqual(base, base.replace())
+
+        i = 0
+        for name, newval in (("hour", 5),
+                             ("minute", 6),
+                             ("second", 7),
+                             ("microsecond", 8),
+                             ("tzinfo", zm200)):
+            newargs = args[:]
+            newargs[i] = newval
+            expected = cls(*newargs)
+            got = base.replace(**{name: newval})
+            self.assertEqual(expected, got)
+            i += 1
+
+        # Ensure we can get rid of a tzinfo.
+        self.assertEqual(base.tzname(), "+100")
+        base2 = base.replace(tzinfo=None)
+        self.failUnless(base2.tzinfo is None)
+        self.failUnless(base2.tzname() is None)
+
+        # Ensure we can add one.
+        base3 = base2.replace(tzinfo=z100)
+        self.assertEqual(base, base3)
+        self.failUnless(base.tzinfo is base3.tzinfo)
+
+        # Out of bounds.
+        base = cls(1)
+        self.assertRaises(ValueError, base.replace, hour=24)
+        self.assertRaises(ValueError, base.replace, minute=-1)
+        self.assertRaises(ValueError, base.replace, second=100)
+        self.assertRaises(ValueError, base.replace, microsecond=1000000)
+
 class TestDateTimeTZ(TestDateTime, TZInfoBase):
     theclass = datetimetz
 
@@ -2157,6 +2269,44 @@
                 self.assertEqual(d.isoformat('k'), datestr + 'k' + tailstr)
                 self.assertEqual(str(d), datestr + ' ' + tailstr)
 
+    def test_replace(self):
+        cls = self.theclass
+        z100 = FixedOffset(100, "+100")
+        zm200 = FixedOffset(timedelta(minutes=-200), "-200")
+        args = [1, 2, 3, 4, 5, 6, 7, z100]
+        base = cls(*args)
+        self.assertEqual(base, base.replace())
+
+        i = 0
+        for name, newval in (("year", 2),
+                             ("month", 3),
+                             ("day", 4),
+                             ("hour", 5),
+                             ("minute", 6),
+                             ("second", 7),
+                             ("microsecond", 8),
+                             ("tzinfo", zm200)):
+            newargs = args[:]
+            newargs[i] = newval
+            expected = cls(*newargs)
+            got = base.replace(**{name: newval})
+            self.assertEqual(expected, got)
+            i += 1
+
+        # Ensure we can get rid of a tzinfo.
+        self.assertEqual(base.tzname(), "+100")
+        base2 = base.replace(tzinfo=None)
+        self.failUnless(base2.tzinfo is None)
+        self.failUnless(base2.tzname() is None)
+
+        # Ensure we can add one.
+        base3 = base2.replace(tzinfo=z100)
+        self.assertEqual(base, base3)
+        self.failUnless(base.tzinfo is base3.tzinfo)
+
+        # Out of bounds.
+        base = cls(2000, 2, 29)
+        self.assertRaises(ValueError, base.replace, year=2001)
 
 def test_suite():
     allsuites = [unittest.makeSuite(klass, 'test')
diff --git a/Modules/datetimemodule.c b/Modules/datetimemodule.c
index 250ee23..6fd10ed 100644
--- a/Modules/datetimemodule.c
+++ b/Modules/datetimemodule.c
@@ -2143,6 +2143,8 @@
 
 /* Constructors. */
 
+static char *date_kws[] = {"year", "month", "day", NULL};
+
 static PyObject *
 date_new(PyTypeObject *type, PyObject *args, PyObject *kw)
 {
@@ -2151,11 +2153,7 @@
 	int month;
 	int day;
 
-	static char *keywords[] = {
-		"year", "month", "day", NULL
-	};
-
-	if (PyArg_ParseTupleAndKeywords(args, kw, "iii", keywords,
+	if (PyArg_ParseTupleAndKeywords(args, kw, "iii", date_kws,
 					&year, &month, &day)) {
 		if (check_date_args(year, month, day) < 0)
 			return NULL;
@@ -2454,6 +2452,26 @@
 				 0, 0, 0, -1);
 }
 
+static PyObject *
+date_replace(PyDateTime_Date *self, PyObject *args, PyObject *kw)
+{
+	PyObject *clone;
+	PyObject *tuple;
+	int year = GET_YEAR(self);
+	int month = GET_MONTH(self);
+	int day = GET_DAY(self);
+
+	if (! PyArg_ParseTupleAndKeywords(args, kw, "|iii:replace", date_kws,
+					  &year, &month, &day))
+		return NULL;
+	tuple = Py_BuildValue("iii", year, month, day);
+	if (tuple == NULL)
+		return NULL;
+	clone = date_new(self->ob_type, tuple, NULL);
+	Py_DECREF(tuple);
+	return clone;
+}
+
 static PyObject *date_getstate(PyDateTime_Date *self);
 
 static long
@@ -2602,6 +2620,9 @@
 	 PyDoc_STR("Return the day of the week represented by the date.\n"
 		   "Monday == 0 ... Sunday == 6")},
 
+	{"replace",     (PyCFunction)date_replace,      METH_KEYWORDS,
+	 PyDoc_STR("Return date with new specified fields.")},
+
 	{"__setstate__", (PyCFunction)date_setstate,	METH_O,
 	 PyDoc_STR("__setstate__(state)")},
 
@@ -2712,6 +2733,11 @@
 
 /* Constructors. */
 
+
+static char *datetime_kws[] = {"year", "month", "day",
+			       "hour", "minute", "second", "microsecond",
+			       NULL};
+
 static PyObject *
 datetime_new(PyTypeObject *type, PyObject *args, PyObject *kw)
 {
@@ -2724,12 +2750,7 @@
 	int second = 0;
 	int usecond = 0;
 
-	static char *keywords[] = {
-		"year", "month", "day", "hour", "minute", "second",
-		"microsecond", NULL
-	};
-
-	if (PyArg_ParseTupleAndKeywords(args, kw, "iii|iiii", keywords,
+	if (PyArg_ParseTupleAndKeywords(args, kw, "iii|iiii", datetime_kws,
 					&year, &month, &day, &hour, &minute,
 					&second, &usecond)) {
 		if (check_date_args(year, month, day) < 0)
@@ -3201,6 +3222,31 @@
 }
 
 static PyObject *
+datetime_replace(PyDateTime_DateTime *self, PyObject *args, PyObject *kw)
+{
+	PyObject *clone;
+	PyObject *tuple;
+	int y = GET_YEAR(self);
+	int m = GET_MONTH(self);
+	int d = GET_DAY(self);
+	int hh = DATE_GET_HOUR(self);
+	int mm = DATE_GET_MINUTE(self);
+	int ss = DATE_GET_SECOND(self);
+	int us = DATE_GET_MICROSECOND(self);
+
+	if (! PyArg_ParseTupleAndKeywords(args, kw, "|iiiiiii:replace",
+					  datetime_kws,
+					  &y, &m, &d, &hh, &mm, &ss, &us))
+		return NULL;
+	tuple = Py_BuildValue("iiiiiii", y, m, d, hh, mm, ss, us);
+	if (tuple == NULL)
+		return NULL;
+	clone = datetime_new(self->ob_type, tuple, NULL);
+	Py_DECREF(tuple);
+	return clone;
+}
+
+static PyObject *
 datetime_timetuple(PyDateTime_DateTime *self)
 {
 	return build_struct_time(GET_YEAR(self),
@@ -3348,6 +3394,9 @@
 	 	   "defaults\n"
 	 	   "to 'T'.")},
 
+	{"replace",     (PyCFunction)datetime_replace,	METH_KEYWORDS,
+	 PyDoc_STR("Return datetime with new specified fields.")},
+
 	{"__setstate__", (PyCFunction)datetime_setstate, METH_O,
 	 PyDoc_STR("__setstate__(state)")},
 
@@ -3457,6 +3506,8 @@
 
 /* Constructors. */
 
+static char *time_kws[] = {"hour", "minute", "second", "microsecond", NULL};
+
 static PyObject *
 time_new(PyTypeObject *type, PyObject *args, PyObject *kw)
 {
@@ -3466,11 +3517,8 @@
 	int second = 0;
 	int usecond = 0;
 
-	static char *keywords[] = {
-		"hour", "minute", "second", "microsecond", NULL
-	};
 
-	if (PyArg_ParseTupleAndKeywords(args, kw, "|iiii", keywords,
+	if (PyArg_ParseTupleAndKeywords(args, kw, "|iiii", time_kws,
 					&hour, &minute, &second, &usecond)) {
 		if (check_time_args(hour, minute, second, usecond) < 0)
 			return NULL;
@@ -3669,6 +3717,28 @@
 	return self->hashcode;
 }
 
+static PyObject *
+time_replace(PyDateTime_Time *self, PyObject *args, PyObject *kw)
+{
+	PyObject *clone;
+	PyObject *tuple;
+	int hh = TIME_GET_HOUR(self);
+	int mm = TIME_GET_MINUTE(self);
+	int ss = TIME_GET_SECOND(self);
+	int us = TIME_GET_MICROSECOND(self);
+
+	if (! PyArg_ParseTupleAndKeywords(args, kw, "|iiii:replace",
+					  time_kws,
+					  &hh, &mm, &ss, &us))
+		return NULL;
+	tuple = Py_BuildValue("iiii", hh, mm, ss, us);
+	if (tuple == NULL)
+		return NULL;
+	clone = time_new(self->ob_type, tuple, NULL);
+	Py_DECREF(tuple);
+	return clone;
+}
+
 static int
 time_nonzero(PyDateTime_Time *self)
 {
@@ -3759,6 +3829,9 @@
 	{"strftime",   	(PyCFunction)time_strftime,	METH_KEYWORDS,
 	 PyDoc_STR("format -> strftime() style string.")},
 
+	{"replace",     (PyCFunction)time_replace,	METH_KEYWORDS,
+	 PyDoc_STR("Return datetime with new specified fields.")},
+
 	{"__setstate__", (PyCFunction)time_setstate,	METH_O,
 	 PyDoc_STR("__setstate__(state)")},
 
@@ -3977,6 +4050,9 @@
  * Constructors.
  */
 
+static char *timetz_kws[] = {"hour", "minute", "second", "microsecond",
+			     "tzinfo", NULL};
+
 static PyObject *
 timetz_new(PyTypeObject *type, PyObject *args, PyObject *kw)
 {
@@ -3987,11 +4063,7 @@
 	int usecond = 0;
 	PyObject *tzinfo = Py_None;
 
-	static char *keywords[] = {
-		"hour", "minute", "second", "microsecond", "tzinfo", NULL
-	};
-
-	if (PyArg_ParseTupleAndKeywords(args, kw, "|iiiiO", keywords,
+	if (PyArg_ParseTupleAndKeywords(args, kw, "|iiiiO", timetz_kws,
 					&hour, &minute, &second, &usecond,
 					&tzinfo)) {
 		if (check_time_args(hour, minute, second, usecond) < 0)
@@ -4078,6 +4150,29 @@
 
 /* Note:  tp_richcompare and tp_hash are inherited from time. */
 
+static PyObject *
+timetz_replace(PyDateTime_TimeTZ *self, PyObject *args, PyObject *kw)
+{
+	PyObject *clone;
+	PyObject *tuple;
+	int hh = TIME_GET_HOUR(self);
+	int mm = TIME_GET_MINUTE(self);
+	int ss = TIME_GET_SECOND(self);
+	int us = TIME_GET_MICROSECOND(self);
+	PyObject *tzinfo = self->tzinfo;
+
+	if (! PyArg_ParseTupleAndKeywords(args, kw, "|iiiiO:replace",
+					  timetz_kws,
+					  &hh, &mm, &ss, &us, &tzinfo))
+		return NULL;
+	tuple = Py_BuildValue("iiiiO", hh, mm, ss, us, tzinfo);
+	if (tuple == NULL)
+		return NULL;
+	clone = timetz_new(self->ob_type, tuple, NULL);
+	Py_DECREF(tuple);
+	return clone;
+}
+
 static int
 timetz_nonzero(PyDateTime_TimeTZ *self)
 {
@@ -4204,6 +4299,9 @@
 	{"dst",		(PyCFunction)timetz_dst,	METH_NOARGS,
 	 PyDoc_STR("Return self.tzinfo.dst(self).")},
 
+	{"replace",     (PyCFunction)timetz_replace,	METH_KEYWORDS,
+	 PyDoc_STR("Return timetz with new specified fields.")},
+
 	{"__setstate__", (PyCFunction)timetz_setstate,	METH_O,
 	 PyDoc_STR("__setstate__(state)")},
 
@@ -4314,6 +4412,11 @@
 	((PyDateTime_DateTimeTZ *)self)->tzinfo = newtzinfo;
 }
 
+static char *datetimetz_kws[] = {
+	"year", "month", "day", "hour", "minute", "second",
+	"microsecond", "tzinfo", NULL
+};
+
 static PyObject *
 datetimetz_new(PyTypeObject *type, PyObject *args, PyObject *kw)
 {
@@ -4327,12 +4430,7 @@
 	int usecond = 0;
 	PyObject *tzinfo = Py_None;
 
-	static char *keywords[] = {
-		"year", "month", "day", "hour", "minute", "second",
-		"microsecond", "tzinfo", NULL
-	};
-
-	if (PyArg_ParseTupleAndKeywords(args, kw, "iii|iiiiO", keywords,
+	if (PyArg_ParseTupleAndKeywords(args, kw, "iii|iiiiO", datetimetz_kws,
 					&year, &month, &day, &hour, &minute,
 					&second, &usecond, &tzinfo)) {
 		if (check_date_args(year, month, day) < 0)
@@ -4572,6 +4670,33 @@
 /* Note:  tp_richcompare and tp_hash are inherited from datetime. */
 
 static PyObject *
+datetimetz_replace(PyDateTime_DateTimeTZ *self, PyObject *args, PyObject *kw)
+{
+	PyObject *clone;
+	PyObject *tuple;
+	int y = GET_YEAR(self);
+	int m = GET_MONTH(self);
+	int d = GET_DAY(self);
+	int hh = DATE_GET_HOUR(self);
+	int mm = DATE_GET_MINUTE(self);
+	int ss = DATE_GET_SECOND(self);
+	int us = DATE_GET_MICROSECOND(self);
+	PyObject *tzinfo = self->tzinfo;
+
+	if (! PyArg_ParseTupleAndKeywords(args, kw, "|iiiiiiiO:replace",
+					  datetimetz_kws,
+					  &y, &m, &d, &hh, &mm, &ss, &us,
+					  &tzinfo))
+		return NULL;
+	tuple = Py_BuildValue("iiiiiiiO", y, m, d, hh, mm, ss, us, tzinfo);
+	if (tuple == NULL)
+		return NULL;
+	clone = datetimetz_new(self->ob_type, tuple, NULL);
+	Py_DECREF(tuple);
+	return clone;
+}
+
+static PyObject *
 datetimetz_timetuple(PyDateTime_DateTimeTZ *self)
 {
 	int dstflag = -1;
@@ -4780,6 +4905,9 @@
 	{"dst",		(PyCFunction)datetimetz_dst, METH_NOARGS,
 	 PyDoc_STR("Return self.tzinfo.dst(self).")},
 
+	{"replace",     (PyCFunction)datetimetz_replace,	METH_KEYWORDS,
+	 PyDoc_STR("Return datetimetz with new specified fields.")},
+
 	{"__setstate__", (PyCFunction)datetimetz_setstate, METH_O,
 	 PyDoc_STR("__setstate__(state)")},