Index: py3k/Doc/library/datetime.rst
===================================================================
--- py3k/Doc/library/datetime.rst	(revision 80032)
+++ py3k/Doc/library/datetime.rst	(working copy)
@@ -982,6 +982,20 @@
       '2002-12-25 00:00:00-06:39'
 
 
+.. method:: datetime.rfcformat()
+
+   Return a string representing the date and time in RFC 3339 format,
+   YYYY-MM-DDTHH:MM:SS.mmmmmm+HH:MM or, if :attr:`microsecond` is 0,
+   YYYY-MM-DDTHH:MM:SS+HH:MM
+
+   This method differs from :meth:`isoformat` in that the separator is
+   always 'T', and the string always contains the UTC offset.  For
+   naive instances the default UTC offset is '-00:00'.  For example,
+
+      >>> datetime(2010, 4, 12).rfcformat()
+      '2010-04-12T00:00:00-00:00'
+
+
 .. method:: datetime.__str__()
 
    For a :class:`datetime` instance *d*, ``str(d)`` is equivalent to
Index: py3k/Lib/test/test_datetime.py
===================================================================
--- py3k/Lib/test/test_datetime.py	(revision 80032)
+++ py3k/Lib/test/test_datetime.py	(working copy)
@@ -1186,6 +1186,23 @@
         # str is ISO format with the separator forced to a blank.
         self.assertEqual(str(t), "0002-03-02 00:00:00")
 
+    def test_rfcformat(self):
+        t = self.theclass(2, 3, 2, 4, 5, 1, 123)
+        self.assertEqual(t.rfcformat(), "0002-03-02T04:05:01.000123-00:00")
+
+        t = self.theclass(2, 3, 2, 4, 5, 1, 0)
+        self.assertEqual(t.rfcformat(), "0002-03-02T04:05:01-00:00")
+
+        t = self.theclass(2, 3, 2)
+        self.assertEqual(t.rfcformat(), "0002-03-02T00:00:00-00:00")
+
+        # with tzinfo:
+        t = self.theclass(2, 3, 2, 4, 5, 1, 123, FixedOffset(0, "UTC"))
+        self.assertEqual(t.rfcformat(), "0002-03-02T04:05:01.000123+00:00")
+
+        t = self.theclass(2, 3, 2, 4, 5, 1, 123, FixedOffset(77, "77min"))
+        self.assertEqual(t.rfcformat(), "0002-03-02T04:05:01.000123+01:17")
+
     def test_format(self):
         dt = self.theclass(2007, 9, 10, 4, 5, 1, 123)
         self.assertEqual(dt.__format__(''), str(dt))
Index: py3k/Modules/datetimemodule.c
===================================================================
--- py3k/Modules/datetimemodule.c	(revision 80032)
+++ py3k/Modules/datetimemodule.c	(working copy)
@@ -4180,6 +4180,38 @@
 }
 
 static PyObject *
+datetime_rfcformat(PyDateTime_DateTime *self)
+{
+	char buffer[100];
+	PyObject *result;
+	int us = DATE_GET_MICROSECOND(self);
+
+	/* We will need the UTC offset. */
+	if (!HASTZINFO(self)) {
+		PyOS_snprintf(buffer, sizeof(buffer), "-00:00");
+	}
+	else if (format_utcoffset(buffer, sizeof(buffer), ":", self->tzinfo,
+			     (PyObject *)self) < 0) {
+		return NULL;
+	}
+
+	if (us)
+		result = PyUnicode_FromFormat("%04d-%02d-%02dT%02d:%02d:%02d.%06d%s",
+		                              GET_YEAR(self), GET_MONTH(self),
+		                              GET_DAY(self),
+		                              DATE_GET_HOUR(self), DATE_GET_MINUTE(self),
+		                              DATE_GET_SECOND(self), us, buffer);
+	else
+		result = PyUnicode_FromFormat("%04d-%02d-%02dT%02d:%02d:%02d%s",
+		                              GET_YEAR(self), GET_MONTH(self),
+		                              GET_DAY(self),
+		                              DATE_GET_HOUR(self), DATE_GET_MINUTE(self),
+		                              DATE_GET_SECOND(self), buffer);
+
+	return result;
+}
+
+static PyObject *
 datetime_ctime(PyDateTime_DateTime *self)
 {
 	return format_ctime((PyDateTime_Date *)self,
@@ -4568,6 +4600,10 @@
 	 	   "sep is used to separate the year from the time, and "
 	 	   "defaults to 'T'.")},
 
+	{"rfcformat",   (PyCFunction)datetime_rfcformat, METH_NOARGS,
+	 PyDoc_STR("Return string in RFC 3339 format, "
+	 	   "YYYY-MM-DDTHH:MM:SS[.mmmmmm]+HH:MM.")},
+
 	{"utcoffset",	(PyCFunction)datetime_utcoffset, METH_NOARGS,
 	 PyDoc_STR("Return self.tzinfo.utcoffset(self).")},