code: def weekdays
        selected = @weekdays.select { |_day, day_selected| day_selected }
        # Ruby 1.8 returns an array for Hash#select and loses order
        return selected.keys if selected.is_a?(Hash)
        selected.map(&:first).sort_by { |v| WEEKDAY_KEYS.index(v) }
      end
docs: Returns array of weekday selected
   e.g. [:sun, :sat]