# File lib/holidays/jp.rb, line 73 def self.jp_national_culture_day(year) day = case year when 1851..1899 22.2588 when 1900..1979 23.2588 when 1980..2099 23.2488 when 2100..2150 24.2488 else raise IndexError.new("Out of range") end day += 0.242194 * (year - 1980) - ((year - 1980)/4).floor day = day.floor Date.civil(year, 9, day) end