if a is date, do nothing
if a is numeric, transform
simple if then statement

yes offcoz... I wanna know what code i can use to determine if it is in a date format or it's a numerical value.

because SAS only have formats of Char and numerical, and DATE is a numerical value as well.

yes offcoz... I wanna know what code i can use to determine if it is in a date format or it's a numerical value.

because SAS only have formats of Char and numerical, and DATE is a numerical value as well.

try this one:

data test;
input a $20.;
if length (trim(a)) = 10 then do;
   year = substr(trim(a),7,4);
   month= substr(trim(a),4,2);
   day  = substr(trim(a),1,2);
   b = mdy(month,day,year);
   end;
if length(trim(a)) = 8 then do;
   year = substr(trim(a),1,4);
   month= substr(trim(a),5,2);
   day  = substr(trim(a),7,2);
   b=mdy(month,day,year);
   end;
cards;
25/05/2001
20000312
19990909
12/01/2009
;
run;
proc print data = test;
var b;
format b yymmdd8.;
run;

output:
Obs           b

                                          1     01-05-25
                                          2     00-03-12
                                          3     99-09-09
                                          4     09-01-12

4# windlove 问题哪有你描述的那么复杂？SAS仅仅有关date的formats 就有几十个。