This is from memory so hope I have it right - no manual either.
Push the RDS button until Hour shows on display. Use Select button to set hour. Push RDS button again until Minute shows on display. Use Select Button to set minutes.
Hope your's works longer than mine. I "fixed" it but only lasted about 3 months and went out again. Haven't been able to get it back. Well, guess that's not quite true, display is real dim and I can see it in the dark.