diff --git a/qinling/db/sqlalchemy/model_base.py b/qinling/db/sqlalchemy/model_base.py
index e7f43809..b988d15f 100644
--- a/qinling/db/sqlalchemy/model_base.py
+++ b/qinling/db/sqlalchemy/model_base.py
@@ -85,7 +85,6 @@ class _QinlingModelBase(oslo_models.ModelBase, oslo_models.TimestampMixin):
         updated_at = getattr(self, 'updated_at')
         if updated_at:
             setattr(m, 'updated_at', updated_at.isoformat(' '))
-
         return m
 
     def __repr__(self):
diff --git a/qinling/tests/unit/api/controllers/v1/test_job.py b/qinling/tests/unit/api/controllers/v1/test_job.py
index 6f052bb4..c2ea6a5a 100644
--- a/qinling/tests/unit/api/controllers/v1/test_job.py
+++ b/qinling/tests/unit/api/controllers/v1/test_job.py
@@ -217,9 +217,12 @@ class TestJobController(base.APITest):
             count=10
         ).id
 
+        next_hour_and_half = datetime.utcnow() + timedelta(hours=1.5)
+        next_two_hours = datetime.utcnow() + timedelta(hours=2)
+
         req_body = {
             'next_execution_time': str(
-                datetime.utcnow() + timedelta(hours=1.5)
+                next_hour_and_half.strftime('%Y-%m-%dT%H:%M:%SZ')
             ),
             'pattern': '1 */1 * * *'
         }
@@ -239,7 +242,9 @@ class TestJobController(base.APITest):
 
         req_body = {
             'status': status.RUNNING,
-            'next_execution_time': str(datetime.utcnow() + timedelta(hours=2)),
+            'next_execution_time': str(
+                next_two_hours.strftime('%Y-%m-%dT%H:%M:%SZ')
+            ),
         }
         resp = self.app.put_json('/v1/jobs/%s' % job_id, req_body)
 
diff --git a/qinling/utils/common.py b/qinling/utils/common.py
index 1c09ca18..5eae1d1a 100644
--- a/qinling/utils/common.py
+++ b/qinling/utils/common.py
@@ -85,7 +85,7 @@ def datetime_to_str(dct, attr_name):
     """Convert datetime object in dict to string."""
     if (dct.get(attr_name) is not None and
             not isinstance(dct.get(attr_name), six.string_types)):
-        dct[attr_name] = dct[attr_name].isoformat(' ')
+        dct[attr_name] = dct[attr_name].strftime('%Y-%m-%dT%H:%M:%SZ')
 
 
 def generate_unicode_uuid(dashed=True):