Calculating leap year

SAS support give out one way to identify leap year:
Sample 44233: Calculating leap year using PROC FCMP and user-defined function

Below is another simple method:

/* check if Febuary has 28 or 29 days in the year */
data _null_;
 do year = 1997 to 2005;
  days = datdif(mdy(2,1,year), mdy(3,1,year), 'act/act');

  if days=29 then leap='Yes';
  else leap='No';

  put year= leap=;
 end;
run;