Try

yyyymmdd10. --> yymmdd10.

104  data one;
105  input Obs Member_id $ date  yymmdd10.  dx ;
106  list;
107  cards;

RULE:      ----+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8----+
108        1 164-234 2005/01/01 250
109        2 297-123 2005/02/03 4952
110        3 164-234 2005/03/15 78910
111        4 297-123 2005/04/14 250
112        5 297-123 2005/08/19 12345
113        6 164-234 2005/09/13 250
114        7 297-123 2005/11/01 4952
NOTE: The data set WORK.ONE has 7 observations and 4 variables.
NOTE: DATA statement used (Total process time):
      real time           0.00 seconds
      cpu time            0.00 seconds


115  ;
116
117  run;
118
119  proc print ;run;