x일 이상 지난 기존 주제를 일괄 닫기?

[Tealk]

@Discourse

Close all topics created before a specified date (includes post action)

Topic.where(closed: false).where("created_at < '2015-01-01'").find_each do |topic| 
  topic.update_status('closed', true, Discourse.system_user)
end

Yes, there would be something similar linked, how can I narrow it down to one category?