Fix cast

django_pg_rrule/managers.py

@@ -88,7 +88,7 @@ class RecurrenceManager(CTEManager):
                     ),
                     default=Func(
                         Value("{}", output_field=ArrayField(DateTimeField())),
-                        F(self.date_start_field),
+                        Cast(self.date_start_field, output_field=DateTimeField()),
                         function="ARRAY_APPEND",
                         output_field=ArrayField(DateTimeField()),
                     ),