let day_of_week (year: int) (month: int) (day: int): int =
    let year: int = if month<3 then year-1 else year in
    let last_two: float = float_of_int (year mod 100) in
    let first_two: float = float_of_int (year /100) in
    let day: float = float_of_int day in
    let month: float = float_of_int month in
    let adjusted_month: float = float_of_int (((int_of_float month +9) mod 12) +1) in
    int_of_float(day +. (2.6 *.adjusted_month -.0.2) +. last_two +. (last_two /.4.0) +. (first_two /.4.0) -. 2.0 *. first_two) mod 7