def start_of_month(year, merch_month)
      # 91 = number of days in a single 4-5-4 set 
      start = start_of_year(year) + ((merch_month - 1) / 3).to_i * 91

      case merch_month
      when  *FOUR_WEEK_MONTHS
        # 28 = 4 weeks
        start = start + 28
      when *FIVE_WEEK_MONTHS
        # The 5 week months
        # 63 = 4 weeks + 5 weeks
        start = start + 63
      end
      
      start
    end
def start_of_month(year, merch_month)
      # 91 = number of days in a single 4-5-4 set 
      start = start_of_year(year) + ((merch_month - 1) / 3).to_i * 91

      case merch_month
      when  *FOUR_WEEK_MONTHS
        # 28 = 4 weeks
        start = start + 28
      when *FIVE_WEEK_MONTHS
        # The 5 week months
        # 63 = 4 weeks + 5 weeks
        start = start + 63
      end
      
      start
    end
The starting date of the given merch month

 @param year [Integer] the retail year
 @param merch_month [Integer] the nth merch month of the retail calendar
 @return [Date] the start date of the merch month