diff --git a/cloudpulse/objects/utils.py b/cloudpulse/objects/utils.py
index 71ad113..82a8b82 100644
--- a/cloudpulse/objects/utils.py
+++ b/cloudpulse/objects/utils.py
@@ -111,7 +111,7 @@ def dt_serializer(name):
     """Return a datetime serializer for a named attribute."""
     def serializer(self, name=name):
         if getattr(self, name) is not None:
-            return timeutils.isotime(getattr(self, name))
+            return datetime.datetime.isoformat(getattr(self, name))
         else:
             return None
     return serializer