Ensure datetime/date are serialized to correct format (#33086)

spec/serializers/rest/account_relationship_severance_event_serializer_spec.rb

@@ -5,7 +5,7 @@ require 'rails_helper'
 RSpec.describe REST::AccountRelationshipSeveranceEventSerializer do
   subject { serialized_record_json(record, described_class) }
 
-  let(:record) { Fabricate.build :account_relationship_severance_event, id: 123 }
+  let(:record) { Fabricate.build :account_relationship_severance_event, id: 123, created_at: DateTime.new(2024, 11, 28, 16, 20, 0) }
 
   describe 'serialization' do
     it 'returns expected values' do
@@ -15,4 +15,10 @@ RSpec.describe REST::AccountRelationshipSeveranceEventSerializer do
         )
     end
   end
+
+  context 'when created_at is populated' do
+    it 'parses as RFC 3339 datetime' do
+      expect { DateTime.rfc3339(subject['created_at']) }.to_not raise_error
+    end
+  end
 end