Show prime day in 2013

primeday.rb

#!/usr/bin/env ruby

require 'prime'

days = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]

(201301..201312).each do |m|
  sd = (m.to_s + "01").to_i
  ed = (m.to_s + days[m % 12].to_s).to_i
  (sd..ed).each do |n|
    puts n if Prime.prime?(n)
  end
end

result.txt

20130203
20130223
20130403
20130413
20130503
20130521
20130527
20130529
20130707
20130829
20130931
20131019
20131103
20131109
20131117
20131129
20131207
20131211
20131217
20131229