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

spec/serializers/rest/admin/account_serializer_spec.rb

@@ -5,6 +5,14 @@ require 'rails_helper'
 RSpec.describe REST::Admin::AccountSerializer do
   subject { serialized_record_json(record, described_class) }
 
+  context 'when created_at is populated' do
+    let(:record) { Fabricate :account, user: Fabricate(:user) }
+
+    it 'parses as RFC 3339 datetime' do
+      expect { DateTime.rfc3339(subject['created_at']) }.to_not raise_error
+    end
+  end
+
   describe 'created_by_application_id' do
     context 'when account is application-created' do
       let(:record) { Fabricate :account, user: Fabricate(:user, created_by_application: application) }