diff --git a/services/schema.py b/services/schema.py
index b4d5a26..af42b0f 100644
--- a/services/schema.py
+++ b/services/schema.py
@@ -1,14 +1,13 @@
-from ariadne import ScalarType, QueryType, MutationType, SubscriptionType
+from ariadne import ScalarType, QueryType, MutationType
 
 datetime_scalar = ScalarType("DateTime")
 
 
 @datetime_scalar.serializer
 def serialize_datetime(value):
-    return value.isoformat()
+    return value.isoformat
 
 
 query = QueryType()
 mutation = MutationType()
-subscription = SubscriptionType()
-resolvers = [query, mutation, subscription, datetime_scalar]
+resolvers = [query, mutation, datetime_scalar]