#!/usr/bin/env ruby
require 'date'

from = DateTime.now
to = DateTime.parse("2013-12-31")

friday = (from..to).inject(0) do |friday, date|
	if date.mday == 13 and date.wday == 5 then
		puts date.strftime('%Y-%m-%d')
		friday + 1
	else
		friday
	end
end

puts friday