Date format

 data ex;

  input startd endd;

  datalnes;

  20180312 20180430

  ;

proc sql;

  select startd, endd, input(put(endd,8.),yymmdd8.) - input(put(startd,8.),yymmdd8.) 

  from ex

  ;quit;

Exact CI for Risk Difference

proc freq;
  table TRT*Y / nocol nopercent riskdiff (cl=(wald exact)) ;
  weight n;
  exact riskdiff;
  run;

/* Newcombe CI */

proc freq;

  table strata*trt*y / riskdiff(cl=newcombe common) alpha=0.05;

run;