From 7827a5b7c29ae71daf0175ce3398115374ceb50e Mon Sep 17 00:00:00 2001
From: Alexander Belopolsky <alexander.belopolsky@gmail.com>
Date: Sun, 6 Sep 2015 13:07:21 -0400
Subject: [PATCH] Closes Issue#22241: timezone.utc name is now plain 'UTC', not
 'UTC-00:00'.

---
 Doc/library/datetime.rst   | 19 ++++++++++++-------
 Lib/datetime.py            |  2 ++
 Lib/test/datetimetester.py |  3 ++-
 Misc/NEWS                  |  2 ++
 Modules/_datetimemodule.c  |  5 +++++
 5 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/Doc/library/datetime.rst b/Doc/library/datetime.rst
index 976cd490003..9a0f93656d9 100644
--- a/Doc/library/datetime.rst
+++ b/Doc/library/datetime.rst
@@ -1734,10 +1734,7 @@ made to civil time.
   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 :meth:`datetime.tzname` method.
 
   .. versionadded:: 3.2
 
@@ -1750,11 +1747,19 @@ made to civil time.
 
 .. 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
+  Name generated from ``offset=timedelta(0)`` is now plain 'UTC', not
+  'UTC+00:00'.
+
+
 .. method:: timezone.dst(dt)
 
   Always returns ``None``.
diff --git a/Lib/datetime.py b/Lib/datetime.py
index 3bf9edc5ada..6b2ac33a327 100644
--- a/Lib/datetime.py
+++ b/Lib/datetime.py
@@ -1920,6 +1920,8 @@ class timezone(tzinfo):
 
     @staticmethod
     def _name_from_offset(delta):
+        if not delta:
+            return 'UTC'
         if delta < timedelta(0):
             sign = '-'
             delta = -delta
diff --git a/Lib/test/datetimetester.py b/Lib/test/datetimetester.py
index b8c9b0db94d..f23add35db2 100644
--- a/Lib/test/datetimetester.py
+++ b/Lib/test/datetimetester.py
@@ -258,7 +258,8 @@ class TestTimeZone(unittest.TestCase):
         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 --git a/Misc/NEWS b/Misc/NEWS
index e88106ae30f..096ab67aa52 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -17,6 +17,8 @@ Core and Builtins
 Library
 -------
 
+- Issue #22241: timezone.utc name is now plain 'UTC', not 'UTC-00:00'. 
+
 - Issue #23517: fromtimestamp() and utcfromtimestamp() methods of
   datetime.datetime now round microseconds to nearest with ties going away from
   zero (ROUND_HALF_UP), as Python 2 and Python older than 3.3, instead of
diff --git a/Modules/_datetimemodule.c b/Modules/_datetimemodule.c
index ae459df8a98..008b733bd3c 100644
--- a/Modules/_datetimemodule.c
+++ b/Modules/_datetimemodule.c
@@ -3267,6 +3267,11 @@ timezone_str(PyDateTime_TimeZone *self)
         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 = '-';