fun number_in_month(dates: (int * int * int) list, month: int) =
  if null dates
  then
    0
  else
    if month = 2
    then
      if (#1 hd(dates)) < 29 andalso (#1 hd(dates)) > 0
      then
        1 + number_in_month(tl dates, month)
      else
        number_in_month(tl dates, month)
    else
      if month < 8 andalso month mod 2 <> 0
      then
        1
      else
        0