diff --git a/django/conf/__init__.py b/django/conf/__init__.py
--- a/django/conf/__init__.py
+++ b/django/conf/__init__.py
@@ -102,7 +102,7 @@
                 new_installed_apps.append(app)
         self.INSTALLED_APPS = new_installed_apps
 
-        if hasattr(time, 'tzset'):
+        if hasattr(time, 'tzset') and hasattr(self, 'TIME_ZONE') and bool(self.TIME_ZONE):
             # Move the time zone info into os.environ. See ticket #2315 for why
             # we don't do this unconditionally (breaks Windows).
             os.environ['TZ'] = self.TIME_ZONE
diff --git a/django/conf/project_template/settings.py b/django/conf/project_template/settings.py
--- a/django/conf/project_template/settings.py
+++ b/django/conf/project_template/settings.py
@@ -23,6 +23,8 @@
 # Local time zone for this installation. Choices can be found here:
 # http://en.wikipedia.org/wiki/List_of_tz_zones_by_name
 # although not all choices may be available on all operating systems.
+# On Unix systems you can set it to None if you want Django don't
+# touch the timezone at all so it stays equal to the server's timezone.
 # If running in a Windows environment this must be set to the same as your
 # system time zone.
 TIME_ZONE = 'America/Chicago'
diff --git a/django/db/backends/postgresql/base.py b/django/db/backends/postgresql/base.py
--- a/django/db/backends/postgresql/base.py
+++ b/django/db/backends/postgresql/base.py
@@ -119,7 +119,8 @@
         set_tz = False
         settings_dict = self.settings_dict
         if self.connection is None:
-            set_tz = True
+            new_conn = True
+            set_tz = hasattr(settings, 'TIME_ZONE') and bool(settings.TIME_ZONE)
             if settings_dict['NAME'] == '':
                 from django.core.exceptions import ImproperlyConfigured
                 raise ImproperlyConfigured("You need to specify NAME in your Django settings file.")
@@ -136,8 +137,9 @@
             self.connection.set_isolation_level(1) # make transactions transparent to all cursors
             connection_created.send(sender=self.__class__)
         cursor = self.connection.cursor()
-        if set_tz:
-            cursor.execute("SET TIME ZONE %s", [settings_dict['TIME_ZONE']])
+        if new_conn:
+            if set_tz:
+                cursor.execute("SET TIME ZONE %s", [settings_dict['TIME_ZONE']])
             if not hasattr(self, '_version'):
                 self.__class__._version = get_version(cursor)
             if self._version[0:2] < (8, 0):
diff --git a/django/db/backends/postgresql_psycopg2/base.py b/django/db/backends/postgresql_psycopg2/base.py
--- a/django/db/backends/postgresql_psycopg2/base.py
+++ b/django/db/backends/postgresql_psycopg2/base.py
@@ -110,10 +110,12 @@
         self.validation = BaseDatabaseValidation(self)
 
     def _cursor(self):
+        new_conn = False
         set_tz = False
         settings_dict = self.settings_dict
         if self.connection is None:
-            set_tz = True
+            new_conn = True
+            set_tz = hasattr(settings, 'TIME_ZONE') and bool(settings.TIME_ZONE)
             if settings_dict['NAME'] == '':
                 from django.core.exceptions import ImproperlyConfigured
                 raise ImproperlyConfigured("You need to specify NAME in your Django settings file.")
@@ -137,8 +139,9 @@
             connection_created.send(sender=self.__class__)
         cursor = self.connection.cursor()
         cursor.tzinfo_factory = None
-        if set_tz:
-            cursor.execute("SET TIME ZONE %s", [settings_dict['TIME_ZONE']])
+        if new_conn:
+            if set_tz:
+                cursor.execute("SET TIME ZONE %s", [settings_dict['TIME_ZONE']])
             if not hasattr(self, '_version'):
                 self.__class__._version = get_version(cursor)
             if self._version[0:2] < (8, 0):
diff --git a/docs/ref/settings.txt b/docs/ref/settings.txt
--- a/docs/ref/settings.txt
+++ b/docs/ref/settings.txt
@@ -1505,29 +1505,40 @@
 
 Default: ``'America/Chicago'``
 
-A string representing the time zone for this installation. `See available choices`_.
-(Note that list of available choices lists more than one on the same line;
-you'll want to use just one of the choices for a given time zone. For instance,
-one line says ``'Europe/London GB GB-Eire'``, but you should use the first bit
-of that -- ``'Europe/London'`` -- as your ``TIME_ZONE`` setting.)
+A string representing the time zone for this installation or ``None``. `See
+available choices`_.  (Note that list of available choices lists more than one
+on the same line; you'll want to use just one of the choices for a given time
+zone. For instance, one line says ``'Europe/London GB GB-Eire'``, but you should
+use the first bit of that -- ``'Europe/London'`` -- as your ``TIME_ZONE``
+setting.)
 
 Note that this is the time zone to which Django will convert all dates/times --
 not necessarily the timezone of the server. For example, one server may serve
 multiple Django-powered sites, each with a separate time-zone setting.
 
+If the ``None`` value is used for this setting. Django will refrain from
+setting the timezone and the server system timezone will be used instead.
+
 Normally, Django sets the ``os.environ['TZ']`` variable to the time zone you
 specify in the ``TIME_ZONE`` setting. Thus, all your views and models will
-automatically operate in the correct time zone. However, if you're manually
-:ref:`manually configuring settings
-<settings-without-django-settings-module>`, Django will *not* touch the ``TZ``
-environment variable, and it'll be up to you to ensure your processes are
-running in the correct environment.
+automatically operate in the correct time zone. However, in the following two
+scenarios:
+
+* If you set this setting to ``None``, as described above
+* If you're using the manual configuration option as described in
+  :ref:`manually configuring settings <settings-without-django-settings-module>`
+
+Django will *not* touch the ``TZ`` environment variable, and it'll be up to you
+to ensure your processes are running in the correct environment.
 
 .. note::
     Django cannot reliably use alternate time zones in a Windows environment.
     If you're running Django on Windows, this variable must be set to match the
     system timezone.
 
+.. versionadded:: 1.2
+    The possibility to set the value of this setting to ``None`` was added.
+
 .. _See available choices: http://www.postgresql.org/docs/8.1/static/datetime-keywords.html#DATETIME-TIMEZONE-SET-TABLE
 
 .. setting:: URL_VALIDATOR_USER_AGENT
