require "date"
#
# dates = (Date.parse("2020/01/01")..Date.parse("2020/01/04")).to_a
# pp dates
# # => [#<Date: 2020-01-01 ((2458850j,0s,0n),+0s,2299161j)>,
# #     #<Date: 2020-01-02 ((2458851j,0s,0n),+0s,2299161j)>,
# #     #<Date: 2020-01-03 ((2458852j,0s,0n),+0s,2299161j)>,
# #     #<Date: 2020-01-04 ((2458853j,0s,0n),+0s,2299161j)>]

puts (Date.parse("2015/01/01")..Date.parse("2015/12/31")).count {
  _1.month == _1.day + _1.day
}