diff -r bf789ae9bde7 Doc/library/datetime.rst
--- a/Doc/library/datetime.rst	Fri Aug 28 10:36:01 2015 +1200
+++ b/Doc/library/datetime.rst	Fri Aug 28 11:40:41 2015 -0400
@@ -1734,10 +1734,7 @@
   otherwise :exc:`ValueError` is raised.
 
   The *name* argument is optional.  If specified it must be a string that
-  is used as the value returned by the ``tzname(dt)`` method.  Otherwise,
-  ``tzname(dt)`` returns a string 'UTCsHH:MM', where s is the sign of
-  *offset*, HH and MM are two digits of ``offset.hours`` and
-  ``offset.minutes`` respectively.
+  will be used as the value returned by the ``tzname(dt)`` method.
 
   .. versionadded:: 3.2
 
@@ -1750,11 +1747,16 @@
 
 .. method:: timezone.tzname(dt)
 
-  Return the fixed value specified when the :class:`timezone` instance is
-  constructed or a string 'UTCsHH:MM', where s is the sign of
-  *offset*, HH and MM are two digits of ``offset.hours`` and
+  Return the fixed value specified when the :class:`timezone` instance
+  is constructed.  If ``name`` is not provided in the constructor, the
+  name returned by ``tzname(dt)`` is generated from the value of the
+  ``offset`` as follows.  If ``offset`` is ``timedelta(0)``, the name
+  is "UTC", otherwise it is a string 'UTC±HH:MM', where ± is the sign
+  of ``offset``, HH and MM are two digits of ``offset.hours`` and
   ``offset.minutes`` respectively.
 
+  .. versionchanged:: 3.6
+  
 .. method:: timezone.dst(dt)
 
   Always returns ``None``.
diff -r bf789ae9bde7 Lib/datetime.py
--- a/Lib/datetime.py	Fri Aug 28 10:36:01 2015 +1200
+++ b/Lib/datetime.py	Fri Aug 28 11:40:41 2015 -0400
@@ -1918,6 +1918,8 @@
 
     @staticmethod
     def _name_from_offset(delta):
+        if not delta:
+            return 'UTC'
         if delta < timedelta(0):
             sign = '-'
             delta = -delta
diff -r bf789ae9bde7 Lib/test/datetimetester.py
--- a/Lib/test/datetimetester.py	Fri Aug 28 10:36:01 2015 +1200
+++ b/Lib/test/datetimetester.py	Fri Aug 28 11:40:41 2015 -0400
@@ -258,7 +258,8 @@
         with self.assertRaises(TypeError): self.EST.dst(5)
 
     def test_tzname(self):
-        self.assertEqual('UTC+00:00', timezone(ZERO).tzname(None))
+        self.assertEqual('UTC', timezone.utc.tzname(None))
+        self.assertEqual('UTC', timezone(ZERO).tzname(None))
         self.assertEqual('UTC-05:00', timezone(-5 * HOUR).tzname(None))
         self.assertEqual('UTC+09:30', timezone(9.5 * HOUR).tzname(None))
         self.assertEqual('UTC-00:01', timezone(timedelta(minutes=-1)).tzname(None))
diff -r bf789ae9bde7 Modules/_datetimemodule.c
--- a/Modules/_datetimemodule.c	Fri Aug 28 10:36:01 2015 +1200
+++ b/Modules/_datetimemodule.c	Fri Aug 28 11:40:41 2015 -0400
@@ -3287,6 +3287,11 @@
         Py_INCREF(self->name);
         return self->name;
     }
+    if (self == PyDateTime_TimeZone_UTC ||
+	(GET_TD_DAYS(self->offset) == 0 &&
+	 GET_TD_SECONDS(self->offset) == 0 &&
+	 GET_TD_MICROSECONDS(self->offset) == 0))
+	return PyUnicode_FromString("UTC");
     /* Offset is normalized, so it is negative if days < 0 */
     if (GET_TD_DAYS(self->offset) < 0) {
         sign = '-';