Index: Misc/NEWS
===================================================================
--- Misc/NEWS	(revision 80840)
+++ Misc/NEWS	(working copy)
@@ -348,6 +348,8 @@
 Library
 -------
 
+- Issue #8644: td.total_seconds() is now equivalent to td / timedelta(seconds=1).
+
 - Issue #4265: shutil.copyfile() was leaking file descriptors when disk fills.
   Patch by Tres Seaver.
 
Index: Doc/library/datetime.rst
===================================================================
--- Doc/library/datetime.rst	(revision 80840)
+++ Doc/library/datetime.rst	(working copy)
@@ -287,8 +287,11 @@
 .. method:: timedelta.total_seconds()
 
    Return the total number of seconds contained in the duration. Equivalent to
-   ``td.microseconds / 1000000 + td.seconds + td.days * 24 * 3600``.
+   ``td / timedelta(seconds=1)``.
 
+   Note that for very large time intervals (greater than 280 years on
+   most platforms) this method will lose microsecond accuracy.
+
    .. versionadded:: 3.2
 
 
Index: Lib/test/test_datetime.py
===================================================================
--- Lib/test/test_datetime.py	(revision 80840)
+++ Lib/test/test_datetime.py	(working copy)
@@ -264,6 +264,11 @@
         for total_seconds in [123456.789012, -123456.789012, 0.123456, 0, 1e6]:
             td = timedelta(seconds=total_seconds)
             self.assertEqual(td.total_seconds(), total_seconds)
+        # Issue8644: Test that td.total_seconds() has the same
+        # accuracy as td / timedelta(seconds=1).
+        for ms in [-1, -2, -123]:
+            td = timedelta(microseconds=ms)
+            self.assertEqual(td.total_seconds(), td / timedelta(seconds=1))
 
     def test_carries(self):
         t1 = timedelta(days=100,
Index: Modules/datetimemodule.c
===================================================================
--- Modules/datetimemodule.c	(revision 80840)
+++ Modules/datetimemodule.c	(working copy)
@@ -2211,9 +2211,25 @@
 static PyObject *
 delta_total_seconds(PyObject *self)
 {
-	return PyFloat_FromDouble(GET_TD_MICROSECONDS(self) / 1000000.0 +
-				  GET_TD_SECONDS(self) +
-				  GET_TD_DAYS(self) * 24.0 * 3600.0);
+	PyObject *total_seconds;
+	PyObject *total_microseconds;
+	PyObject *one_million;
+
+	total_microseconds = delta_to_microseconds((PyDateTime_Delta *)self);
+	if (total_microseconds == NULL)
+		return NULL;
+
+	one_million = PyLong_FromLong(1000000L);
+	if (one_million == NULL) {
+		Py_DECREF(total_microseconds);
+		return NULL;
+	}
+
+	total_seconds = PyNumber_TrueDivide(total_microseconds, one_million);
+
+	Py_DECREF(total_microseconds);
+	Py_DECREF(one_million);
+	return total_seconds;
 }
 
 static PyObject *