很繁琐......
期待好办法

我也是这么写的，以为有个函数可以直接解决的，期待简单方法

proc format;
    invalue days "01","03","05","07","08","10","12"=31
                             "04","06","09","11"=30
                             "02"=28;
run;

data test;
    input yymm $;
        cards;
200808
200802
200002
201002
198712
200304
;

data wanted;
     set test;
    y=substr(yymm,1,4);
    m=substr(yymm,5);
    d=input(m,days.);
    if mod(y,400)=0  or (mod(y,4)=0 and mod(y,100)^=0) then d=ifn(m="02",d+1,d);
run;

proc format;
    invalue days "01","03","05","07","08","10","12"=31
                             "04","06","09","11"=30
                             "02"=28;
run;

data test;
    input yymm $;
        cards;
200808
200802
200002
201002
198712
200304
;

data wanted;
     set test;
    y=substr(yymm,1,4);
    m=substr(yymm,5);
    d=input(m,days.);
    if m="02" and (mdy(12,31,y)-mdy(1,1,y)+1=366) then d=d+1;
run;