# File lib/ice_cube/time_util.rb, line 172
    def self.wday_to_sym(wday)
      return wday if DAYS.keys.include? wday
      DAYS.invert.fetch(wday) do |i|
        raise ArgumentError, "Expecting Integer value for weekday. " \
                             "No such wday number: #{i.inspect}"
      end
    end