(define (how-many-days-hours-minutes-seconds n)
  (let* ((days     (quotient n seconds-in-a-day))
         (n-rest-1 (modulo n seconds-in-a-day))
         (hours    (quotient n-rest-1 seconds-in-an-hour))
         (n-rest-2 (modulo n-rest-1 seconds-in-an-hour))
         (minutes  (quotient n-rest-2 60))
         (seconds  (modulo n-rest-2 60))
        ) 
    (list days hours minutes seconds)))