In reply to Bruce Gilsen.

Thank you, Bruce. Indeed, there is DATDIF() function in MS Excel, but DATDIF4_SLK() function in SAS. The original DATDIF() function has 3 arguments (3rd argument is unit - DAY, MONTH, YEAR,...), however, DATDIF4_SLK has only 2 arguments as it implements a subset of DATDIF() for DAYS only. I made corresponding correction in the table and added NOTE to it.