require 'date'

a = Date.new(2015, 1, 1)
b = Date.new(2015, 12, 31)

def happy_days(a, b)
  (a..b).count { |c|
    c.month == c.day.to_s.split('').map(&:to_i).inject(:+)
  }
end

puts happy_days(a, b)