(define (day-of-week day month year)
  (let* ((x (quotient (- 14 month) 12))
         (y (- year x))
         (z (- (+ month (* 12 x)) 2)))
    (remainder (+ 7000 (+ day (+ y (+ (quotient y 4) (+ (quotient y 400) (- (quotient(* 31 z) 12) (quotient y 100) )))))) 7)))