def last_modified
      rails_root_mtime = Time.zone.at(::File.new("#{Rails.root}").mtime)
      timestamps = [rails_root_mtime, self.updated_at]
      timestamps.sort.last
    end
def last_modified
      rails_root_mtime = Time.zone.at(::File.new("#{Rails.root}").mtime)
      timestamps = [rails_root_mtime, self.updated_at]
      timestamps.sort.last
    end
Return the logical modification time for the element.