diff --git a/oslo_serialization/jsonutils.py b/oslo_serialization/jsonutils.py
index f24adbe..3d326e7 100644
--- a/oslo_serialization/jsonutils.py
+++ b/oslo_serialization/jsonutils.py
@@ -57,6 +57,7 @@ else:
 
 from oslo_utils import encodeutils
 from oslo_utils import importutils
+from oslo_utils import timeutils
 import six
 import six.moves.xmlrpc_client as xmlrpclib
 
@@ -110,7 +111,7 @@ def to_primitive(value, convert_instances=False, convert_datetime=True,
 
     if isinstance(value, datetime.datetime):
         if convert_datetime:
-            return value.isoformat()
+            return timeutils.strtime(value)
         else:
             return value
 
diff --git a/oslo_serialization/tests/test_jsonutils.py b/oslo_serialization/tests/test_jsonutils.py
index 18bdc36..9709cb6 100644
--- a/oslo_serialization/tests/test_jsonutils.py
+++ b/oslo_serialization/tests/test_jsonutils.py
@@ -17,7 +17,6 @@ import collections
 import datetime
 import json
 
-import iso8601
 import mock
 import netaddr
 from oslo_i18n import fixture
@@ -136,12 +135,6 @@ class ToPrimitiveTestCase(test_base.BaseTestCase):
         self.assertEqual(jsonutils.to_primitive(x),
                          '1920-02-03T04:05:06.000007')
 
-    def test_datetime_timezone(self):
-        x = datetime.datetime(1920, 2, 3, 4, 5, 6, 7,
-                              tzinfo=iso8601.iso8601.UTC)
-        self.assertEqual(jsonutils.to_primitive(x),
-                         '1920-02-03T04:05:06.000007+00:00')
-
     def test_datetime_preserve(self):
         x = datetime.datetime(1920, 2, 3, 4, 5, 6, 7)
         self.assertEqual(jsonutils.to_primitive(x, convert_datetime=False), x)
@@ -150,7 +143,7 @@ class ToPrimitiveTestCase(test_base.BaseTestCase):
         x = xmlrpclib.DateTime()
         x.decode("19710203T04:05:06")
         self.assertEqual(jsonutils.to_primitive(x),
-                         '1971-02-03T04:05:06')
+                         '1971-02-03T04:05:06.000000')
 
     def test_iter(self):
         class IterClass(object):
diff --git a/tests/test_jsonutils.py b/tests/test_jsonutils.py
index a150b43..d2a7950 100644
--- a/tests/test_jsonutils.py
+++ b/tests/test_jsonutils.py
@@ -173,7 +173,7 @@ class ToPrimitiveTestCase(test_base.BaseTestCase):
         x = xmlrpclib.DateTime()
         x.decode("19710203T04:05:06")
         self.assertEqual(jsonutils.to_primitive(x),
-                         '1971-02-03T04:05:06')
+                         '1971-02-03T04:05:06.000000')
 
     def test_iter(self):
         class IterClass(object):