From 2ec151e35da93047acfeea1b79c27010f2cb8594 Mon Sep 17 00:00:00 2001
From: Tim Graham <timograham@gmail.com>
Date: Thu, 28 Jun 2018 09:26:41 -0400
Subject: Fixed #29514 -- Reverted "Used datetime.timezone.utc instead of
 pytz.utc for better performance."

This reverts commit 27ca5ce19f5f184018a61611c1bc319113b1d107 due to a
regression.
---
 django/utils/feedgenerator.py |  3 ++-
 django/utils/timezone.py      | 14 ++++++++------
 2 files changed, 10 insertions(+), 7 deletions(-)

(limited to 'django/utils')

diff --git a/django/utils/feedgenerator.py b/django/utils/feedgenerator.py
index 319a017e8c..e49f534a19 100644
--- a/django/utils/feedgenerator.py
+++ b/django/utils/feedgenerator.py
@@ -173,7 +173,8 @@ class SyndicationFeed:
                     if latest_date is None or item_date > latest_date:
                         latest_date = item_date
 
-        return latest_date or datetime.datetime.now(utc)
+        # datetime.now(tz=utc) is slower, as documented in django.utils.timezone.now
+        return latest_date or datetime.datetime.utcnow().replace(tzinfo=utc)
 
 
 class Enclosure:
diff --git a/django/utils/timezone.py b/django/utils/timezone.py
index 9870cd03a9..c1f0d70bc1 100644
--- a/django/utils/timezone.py
+++ b/django/utils/timezone.py
@@ -2,10 +2,9 @@
 Timezone-related classes and functions.
 """
 
-import datetime
 import functools
 from contextlib import ContextDecorator
-from datetime import timedelta, tzinfo
+from datetime import datetime, timedelta, tzinfo
 from threading import local
 
 import pytz
@@ -53,8 +52,7 @@ class FixedOffset(tzinfo):
 
 
 # UTC time zone as a tzinfo instance.
-# (Use utc = datetime.timezone.utc here when PY35 isn't supported.)
-utc = datetime.timezone(ZERO, 'UTC')
+utc = pytz.utc
 
 
 def get_fixed_timezone(offset):
@@ -174,7 +172,7 @@ def template_localtime(value, use_tz=None):
     This function is designed for use by the template engine.
     """
     should_convert = (
-        isinstance(value, datetime.datetime) and
+        isinstance(value, datetime) and
         (settings.USE_TZ if use_tz is None else use_tz) and
         not is_naive(value) and
         getattr(value, 'convert_to_local_time', True)
@@ -221,7 +219,11 @@ def now():
     """
     Return an aware or naive datetime.datetime, depending on settings.USE_TZ.
     """
-    return datetime.datetime.now(utc if settings.USE_TZ else None)
+    if settings.USE_TZ:
+        # timeit shows that datetime.now(tz=utc) is 24% slower
+        return datetime.utcnow().replace(tzinfo=utc)
+    else:
+        return datetime.now()
 
 
 # By design, these four functions don't perform any checks on their arguments.
-- 
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