How to generate a random number in Scheme.

I couldn't find a function that generates a random number.
Instead, I make that function using "".

I wont to get current time for a seed.
But I couldn't a function for it.

(define (rand seed)
  (let ((x seed))
    (lambda ()
      (set! x (remainder (+ (* 13 x) 5) 24))
      x)))

(define a (rand 1))

(display (a))
(newline)
(display (a))
(newline)
(display (a))
(newline)

18
23
16