@Susanknoll727 wrote: Thank you . Does this mean I would code for those three observations? Modify your existing code / if AgeAtVisit= 0 then AgeAtVisit = intck(‘dtDay’,VisitDate,DOB); to if AgeAtVisit= 0 then AgeAtVisit = intck('year',VisitDate,DOB,'C');   Note your existing code has a second problem which may indicate you copied the DTDAY option from some other source and that is the presences of the curly or "smart" quotes. Please note the highlighted quotes in the first code that I colored red and made large. Those are not acceptable in SAS code for use in quoting. You have to replace them with the typed quote or double-quote character from your keyboard. Copying code from websites or files opened in anything except plain text or programming editors is the most likely source of the incompatible characters. So watch out for such.   Note: Saying "doesn't work" or similar really requires showing the LOG from what didn't happen. Otherwise we have no idea what code was submitted or what issues SAS may have objected to. ... View more