From ad88524e4db91dc2f148cf40184a81a454ee7aac Mon Sep 17 00:00:00 2001
From: Aymeric Augustin <aymeric.augustin@m4x.org>
Date: Sat, 20 Jul 2019 18:31:47 +0200
Subject: [PATCH] Refs #23524 -- Unified BaseDatabaseWrapper.timezone.

There was a special case in this property to return None when the
database backend supports time zone. However, only the PostgreSQL
backend supports time zones and it never uses this property.
---
 django/db/backends/base/base.py | 17 ++++++++++-------
 docs/releases/3.1.txt           |  5 +++++
 2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/django/db/backends/base/base.py b/django/db/backends/base/base.py
index 9a4c27f0f33..08d5f755aae 100644
--- a/django/db/backends/base/base.py
+++ b/django/db/backends/base/base.py
@@ -117,18 +117,21 @@ class BaseDatabaseWrapper:
     @cached_property
     def timezone(self):
         """
-        Time zone for datetimes stored as naive values in the database.
+        Return a tzinfo of the database connection time zone.
 
-        Return a tzinfo object or None.
+        This is only used when time zone support is enabled. When a datetime is
+        read from the database, it is always returned in this time zone.
 
-        This is only needed when time zone support is enabled and the database
-        doesn't support time zones. (When the database supports time zones,
-        the adapter handles aware datetimes so Django doesn't need to.)
+        When the database backend supports time zones, it doesn't matter which
+        time zone Django uses, as long as aware datetimes are used everywhere.
+        For simplicity, Django selects UTC.
+
+        When the database backend doesn't support time zones, the time zone
+        Django uses can be selected with the TIME_ZONE configuration option, so
+        it can match what other users of the database expect.
         """
         if not settings.USE_TZ:
             return None
-        elif self.features.supports_timezones:
-            return None
         elif self.settings_dict['TIME_ZONE'] is None:
             return timezone.utc
         else:
diff --git a/docs/releases/3.1.txt b/docs/releases/3.1.txt
index b4179883ab1..58f14e172d9 100644
--- a/docs/releases/3.1.txt
+++ b/docs/releases/3.1.txt
@@ -297,6 +297,11 @@ backends.
 * ``DatabaseOperations.fetch_returned_insert_columns()`` now requires an
   additional ``returning_params`` argument.
 
+* ``connection.timezone`` property is now ``'UTC'`` by default, or the
+  :setting:`TIME_ZONE <DATABASE-TIME_ZONE>` when :setting:`USE_TZ` is ``True``
+  on databases that support time zones. Previously, it was ``None`` on
+  databases that support time zones.
+
 Dropped support for MariaDB 10.1
 --------------------------------