/************************************************
create interview date and age on DOI;
  int_m                  CV_INTERVIEW_DATE~M
  int_y                  CV_INTERVIEW_DATE~Y
  AGEM                   CV_AGE_MONTHS_INT_DATE
  AGEYR                  CV_AGE_INT_DATE
  int_cm                 CV_INTERVIEW_CMONTH
************************************************/

/***********************************************************
**  QNAME                                   Variable Name **
    SYMBOL_CURDATE~M_2021                   INT_M
    SYMBOL_CURDATE~Y_2021                   INT_Y
    SYMBOL_KEY_BDATE~M_2021                 BDATE_M
    SYMBOL_KEY_BDATE~Y_2021                 BDATE_Y

*************************************************************/

***** Create AGEM, R's age in month;
if ( int_y>0 and bdate_y>0 and int_m>0 and bdate_m>0) then
   AGEM= (int_y-bdate_y)*12+ (int_m-bdate_m) ;
else AGEM=.;

***** Create AGEYR, R's age in year;
if (int_m>0 and int_y>0 and bdate_m>0 and bdate_y>0) then do;
   if int_m>bdate_m then AGEYR=int_y-bdate_y;
   else if int_m<=bdate_m then AGEYR=int_y-bdate_y-1;
end;
else AGEYR=.;

/* Create int_cm, interview date in continous month. */
if (int_y >0 and int_m>0 ) then int_cm=int_m+12*(int_y-1980);
else int_cm=.;

/* Taking care of non interviewers. */
if  INT_Y =-5  then do;
   INT_m =-5;
   INT_Y =-5;
   int_cm=-5;
   bdate_m=-5;
   bdate_y=-5;
   AGEM=-5;
   AGEYR=-5;
end;

***** generate the output data;
filename out 'out_int_dateR20.dat';

data null;
 set two;
 file out lrecl=70 recfm=v dlm=',' dsd;
 put norcid int_m int_y AGEYR AGEM int_cm;
run;