diff --git a/atmosphere/api/ingress.py b/atmosphere/api/ingress.py
index a369d84..30809b6 100644
--- a/atmosphere/api/ingress.py
+++ b/atmosphere/api/ingress.py
@@ -48,7 +48,9 @@ def event():
 
         try:
             models.Resource.get_or_create(event_data)
-        except (exceptions.EventTooOld, exceptions.IgnoredEvent):
-            return '', 202
+        except exceptions.EventTooOld:
+            return 'Event Too Old', 202
+        except exceptions.IgnoredEvent:
+            return 'Ignored Event', 202
 
     return '', 204
diff --git a/atmosphere/api/usage.py b/atmosphere/api/usage.py
index 103815a..df89c92 100644
--- a/atmosphere/api/usage.py
+++ b/atmosphere/api/usage.py
@@ -15,7 +15,7 @@
 """Usage API."""
 
 import os
-from datetime import datetime
+import dateutil.parser
 
 from flask import abort
 from flask import Blueprint
@@ -65,8 +65,8 @@ def list_resources():
         project_id = request.args['project_id']
 
     try:
-        start = datetime.fromisoformat(request.args['start'])
-        end = datetime.fromisoformat(request.args['end'])
+        start = dateutil.parser.isoparse(request.args['start'])
+        end = dateutil.parser.isoparse(request.args['end'])
     except (KeyError, ValueError):
         abort(400)
 
diff --git a/atmosphere/models.py b/atmosphere/models.py
index ffca1dc..9cfe581 100644
--- a/atmosphere/models.py
+++ b/atmosphere/models.py
@@ -31,7 +31,11 @@ from sqlalchemy import or_
 
 from atmosphere import exceptions
 
-db = SQLAlchemy()
+session_options = {
+    'autocommit': False
+}
+
+db = SQLAlchemy(session_options=session_options)
 migrate = Migrate()
 
 
@@ -180,7 +184,8 @@ class Resource(db.Model, GetOrCreateMixin):
         # No existing period, start our first period.
         if len(resource.periods) == 0:
             resource.periods.append(Period(
-                started_at=event['traits']['created_at'],
+                started_at=event['traits'].get('created_at') or
+                event['traits'].get('launched_at'),
                 spec=spec
             ))
 
@@ -246,6 +251,12 @@ class Instance(Resource):
         if vm_state_is_deleted and no_deleted_at:
             return True
 
+        # Check if event is missing both created_at and launched_at traits
+        no_created_at = ('created_at' not in event['traits'])
+        no_launched_at = ('launched_at' not in event['traits'])
+        if no_created_at and no_launched_at:
+            return True
+
         return False