使用PROC TRANSPOSE过程步对数据集进行转置时如何保持日期变量的时间顺序

proc transpose data=test out=outx1 (drop=_name_);
by id;
var amount;
id sasdate;
idlabel sasdate;
run;

proc sort data=test;
by id sasdate;
run;
proc sql noprint;
select distinct cats('_',put(sasdate,date9.))
into :alldates separated by ' '
from test
order by sasdate;
quit;
%put &alldates;
data outx1;
retain id &alldates;
set outx1;
run;