You are looking for a macro then.  %macro repeat (max=) ; %do i = 1 %to &max ; pay_0&i= round(coalesce(gross_0&i,0) + coalesce(pension_0&i,0) + coalesce(nic_0&i,0) , 0.01) ; %end ; %mend repeat ; %repeat (max=6) ; ... View more

You need the INTNX function and increment by 0 months but advance it to the beginning of the month.   data have ; input havedate:mmddyy10. ; cards ; 01/04/2017 02/01/2017 04/20/2017 ; run ; data want ; set have ; format havedate wantdate mmddyy10. ; wantdate = intnx("month",havedate,0,"b") ; run ; proc print ; run ; Obs havedate wantdate 1 01/04/2017 01/01/2017 2 02/01/2017 02/01/2017 3 04/20/2017 04/01/2017 ... View more

One way to trick this is to define a character variable that does not hold any more than 10 spaces to fully accommodate YYYY-MM-DD. Then you can append "-01-01". Only partial dates will be able to add the extra values.      data have ; length havedateC $15 ; havedateC = "2020-05-29" ; output ; havedateC = "2020-05" ; output ; havedateC = "2020" ; output ; run ; data want ; set have ; length fulldateC $10 ; fulldateC = strip(havedateC)||"-01-01" ; fulldateN = input(fulldateC,yymmdd10.) ; format fulldateN yymmdd10. ; run ; proc print ; run ;   Obs havedateC fulldateC fulldateN 1 2020-05-29 2020-05-29 2020-05-29 2 2020-05 2020-05-01 2020-05-01 3 2020 2020-01-01 2020-01-01   ... View more

Can you add a few IDs or more rows for the same ID with examples of multiple durations. Present other situations that could be more complex etc.. ... View more