diff -r 3fd9970d9e65 Modules/_datetimemodule.c
--- a/Modules/_datetimemodule.c	Sat Feb 23 19:56:15 2013 +0100
+++ b/Modules/_datetimemodule.c	Sat Feb 23 21:27:08 2013 +0100
@@ -3846,6 +3846,76 @@
     return result;
 }
 
+/*
+ * time arithmetic.
+ */
+
+/* factor must be 1 (to add) or -1 (to subtract).  The result inherits
+ * the tzinfo state of date.
+ */
+static PyObject *
+add_time_timedelta(PyDateTime_Time *time, PyDateTime_Delta *delta,
+                       int factor)
+{
+    /* Note that the C-level additions can't overflow, because of
+     * invariant bounds on the member values.
+     */
+    int day = 0; // Used for normalize_pair
+    int hour = TIME_GET_HOUR(time);
+    int minute = TIME_GET_MINUTE(time);
+    int second = TIME_GET_SECOND(time) + GET_TD_SECONDS(delta) * factor;
+    int microsecond = TIME_GET_MICROSECOND(time) +
+                      GET_TD_MICROSECONDS(delta) * factor;
+
+    assert(factor == 1 || factor == -1);
+
+    normalize_pair(&second, &microsecond, 1000000);
+    normalize_pair(&minute, &second, 60);
+    normalize_pair(&hour, &minute, 60);
+    normalize_pair(&day, &hour, 24);
+
+    return new_time(hour, minute, second, microsecond,
+                            HASTZINFO(time) ? time->tzinfo : Py_None);
+}
+
+static PyObject *
+time_add(PyObject *left, PyObject *right)
+{
+    if (PyTime_Check(left)) {
+        /* time + ??? */
+        if (PyDelta_Check(right))
+            /* time + delta */
+            return add_time_timedelta(
+                            (PyDateTime_Time *)left,
+                            (PyDateTime_Delta *)right,
+                            1);
+    }
+    else if (PyDelta_Check(left)) {
+        /* delta + datetime */
+        return add_time_timedelta((PyDateTime_Time *) right,
+                                      (PyDateTime_Delta *) left,
+                                      1);
+    }
+    Py_INCREF(Py_NotImplemented);
+    return Py_NotImplemented;
+}
+
+static PyObject *
+time_subtract(PyObject *left, PyObject *right)
+{
+    if (PyTime_Check(left)) {
+        /* time + ??? */
+        if (PyDelta_Check(right))
+            /* time + delta */
+            return add_time_timedelta(
+                            (PyDateTime_Time *)left,
+                            (PyDateTime_Delta *)right,
+                            -1);
+    }
+    Py_INCREF(Py_NotImplemented);
+    return Py_NotImplemented;
+}
+
 static PyObject *
 time_reduce(PyDateTime_Time *self, PyObject *arg)
 {
@@ -3889,8 +3959,8 @@
 a tzinfo subclass. The remaining arguments may be ints or longs.\n");
 
 static PyNumberMethods time_as_number = {
-    0,                                          /* nb_add */
-    0,                                          /* nb_subtract */
+    time_add,                                   /* nb_add */
+    time_subtract,                              /* nb_subtract */
     0,                                          /* nb_multiply */
     0,                                          /* nb_remainder */
     0,                                          /* nb_divmod */