diff --git a/almanachclient/commands/update_instance_entity.py b/almanachclient/commands/update_instance_entity.py
index 2ea16b5..bd84311 100644
--- a/almanachclient/commands/update_instance_entity.py
+++ b/almanachclient/commands/update_instance_entity.py
@@ -39,10 +39,10 @@ class UpdateInstanceEntityCommand(ShowOne):
         params = dict()
 
         if parsed_args.start:
-            params['start'] = parser.parse(parsed_args.start)
+            params['start_date'] = parser.parse(parsed_args.start)
 
         if parsed_args.end:
-            params['end'] = parser.parse(parsed_args.end)
+            params['end_date'] = parser.parse(parsed_args.end)
 
         if parsed_args.flavor:
             params['flavor'] = parsed_args.flavor
diff --git a/almanachclient/tests/commands/test_update_instance_entity.py b/almanachclient/tests/commands/test_update_instance_entity.py
index 5e8617b..a873863 100644
--- a/almanachclient/tests/commands/test_update_instance_entity.py
+++ b/almanachclient/tests/commands/test_update_instance_entity.py
@@ -52,4 +52,4 @@ class TestUpdateInstanceEntityCommand(base.TestCase):
         self.assertEqual(expected, self.command.take_action(self.args))
 
         self.client.update_instance_entity.assert_called_once_with(self.args.instance_id,
-                                                                   start=datetime.datetime(2017, 1, 1, 0, 0))
+                                                                   start_date=datetime.datetime(2017, 1, 1, 0, 0))
diff --git a/almanachclient/v1/client.py b/almanachclient/v1/client.py
index 6bb8e26..0d09064 100644
--- a/almanachclient/v1/client.py
+++ b/almanachclient/v1/client.py
@@ -270,8 +270,8 @@ class Client(HttpClient):
         """Update an instance entity.
 
         :arg str instance_id: Instance UUID
-        :arg datetime start: Start date
-        :arg datetime end: End date
+        :arg datetime start_date: Start date
+        :arg datetime end_date: End date
         :arg str flavor: The flavor
         :arg str name: The instance name
         :raises: ClientError
@@ -279,7 +279,7 @@ class Client(HttpClient):
         """
         url = '{}/{}/entity/instance/{}'.format(self.url, self.api_version, instance_id)
 
-        for param in ['start', 'end']:
+        for param in ['start_date', 'end_date']:
             if param in kwargs:
                 kwargs[param] = self._format_body_datetime(kwargs[param])