Use put function to convert num to char.

533  data tmp;
534    date_num=1;
535    date_char=put(date_num, date9.);
536
537    put date_num= date_num= date9.
538    /// date_char=;
539  run;

date_num=1 date_num=02JAN1960


date_char=02JAN1960
NOTE: The data set WORK.TMP has 1 observations and 2 variables.
NOTE: DATA statement used (Total process time):
      real time           0.03 seconds
      cpu time            0.00 seconds

thank you. that is very helpful