diff --git a/ceilometer/tests/pipeline_base.py b/ceilometer/tests/pipeline_base.py
index 3338ecb715..16fe651e7c 100644
--- a/ceilometer/tests/pipeline_base.py
+++ b/ceilometer/tests/pipeline_base.py
@@ -1717,7 +1717,7 @@ class BasePipelineTestCase(base.BaseTestCase):
 
         for offset in range(2):
             counter = copy.copy(self.test_counter)
-            counter.timestamp = timeutils.isotime(counter_time)
+            counter.timestamp = datetime.datetime.isoformat(counter_time)
             counter.resource_id = resource_id[0]
             counter.volume = offset
             counter.type = sample.TYPE_CUMULATIVE
@@ -1732,13 +1732,13 @@ class BasePipelineTestCase(base.BaseTestCase):
         aggregated_counters = aggregator.flush()
         self.assertEqual(len(aggregated_counters), 1)
         self.assertEqual(aggregated_counters[0].timestamp,
-                         timeutils.isotime(test_time))
+                         datetime.datetime.isoformat(test_time))
 
         rate_of_change_transformer.handle_sample(aggregated_counters[0])
 
         for offset in range(2):
             counter = copy.copy(self.test_counter)
-            counter.timestamp = timeutils.isotime(counter_time)
+            counter.timestamp = datetime.datetime.isoformat(counter_time)
             counter.resource_id = resource_id[offset]
             counter.volume = 2
             counter.type = sample.TYPE_CUMULATIVE
@@ -1758,7 +1758,7 @@ class BasePipelineTestCase(base.BaseTestCase):
                 rateOfChange = rate_of_change_transformer.handle_sample(
                     counter)
                 self.assertEqual(counter.timestamp,
-                                 timeutils.isotime(test_time))
+                                 datetime.datetime.isoformat(test_time))
 
         self.assertEqual(rateOfChange.volume, 1)
 
diff --git a/ceilometer/tests/unit/transformer/test_conversions.py b/ceilometer/tests/unit/transformer/test_conversions.py
index 702f0f67b6..c5bc058724 100644
--- a/ceilometer/tests/unit/transformer/test_conversions.py
+++ b/ceilometer/tests/unit/transformer/test_conversions.py
@@ -13,6 +13,7 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 import copy
+import datetime
 
 from oslo_utils import timeutils
 from oslotest import base
@@ -109,6 +110,6 @@ class AggregatorTransformerTestCase(base.BaseTestCase):
         for _ in range(100):
             sample = copy.copy(self.SAMPLE)
             sample.resource_id = sample.resource_id + str(self._sample_offset)
-            sample.timestamp = timeutils.isotime()
+            sample.timestamp = datetime.datetime.isoformat(timeutils.utcnow())
             aggregator.handle_sample(sample)
             self._sample_offset += 1