fixes https://code.djangoproject.com/ticket/18465

django/db/backends/oracle/base.py

@@ -482,9 +482,13 @@ def _cursor(self):
             # Set oracle date to ansi date format.  This only needs to execute
             # once when we create a new connection. We also set the Territory
             # to 'AMERICA' which forces Sunday to evaluate to a '1' in TO_CHAR().
+            cursor.execute("ALTER SESSION SET NLS_TERRITORY = 'AMERICA'")
+            # We set the territory first, which overrides NLS_DATE_FORMAT and
+            # NLS_TIMESTAMP_FORMAT to the territory default, and then set
+            # the formats for predictable behaviour.
+            # see http://docs.oracle.com/cd/E11882_01/server.112/e10729/ch3globenv.htm#autoId14
             cursor.execute("ALTER SESSION SET NLS_DATE_FORMAT = 'YYYY-MM-DD HH24:MI:SS'"
                            " NLS_TIMESTAMP_FORMAT = 'YYYY-MM-DD HH24:MI:SS.FF'"
-                           " NLS_TERRITORY = 'AMERICA'"
                            + (" TIME_ZONE = 'UTC'" if settings.USE_TZ else ''))
 
             if 'operators' not in self.__dict__:

tests/regressiontests/backends/tests.py

@@ -65,6 +65,27 @@ def test_client_encoding(self):
         connection.cursor()  # Ensure the connection is initialized.
         self.assertEqual(connection.connection.encoding, "UTF-8")
         self.assertEqual(connection.connection.nencoding, "UTF-8")
+
+    @unittest.skipUnless(connection.vendor == 'oracle',
+                         "No need to check Oracle connection semantics")
+    def test_order_of_nls_parameters(self):
+        # an 'almost right' datetime should work with configured
+        # NLS parameters as per #18465.
+        c = connection.cursor()
+        query = "select 1 from dual where '1936-12-29 00:00' < sysdate"
+        c.execute(query)
+        try:
+            # should change the NLS_DATE_FORMAT and NLS_TIMESTAMP_FORMAT
+            c.execute("ALTER SESSION SET NLS_TERRITORY = 'AMERICA'")
+            with self.assertRaises(DatabaseError):
+                c.execute(query)
+        finally:
+            try:
+                c.execute("ALTER SESSION SET NLS_DATE_FORMAT = 'YYYY-MM-DD HH24:MI:SS'"
+                          " NLS_TIMESTAMP_FORMAT = 'YYYY-MM-DD HH24:MI:SS.FF'"
+                          + (" TIME_ZONE = 'UTC'" if settings.USE_TZ else ''))
+            except:
+                pass
 
 class MySQLTests(TestCase):
     @unittest.skipUnless(connection.vendor == 'mysql',