Thank you for your suggestion. I used a combination of lag and dif functions to get the answer I was looking for.   My dataset looked like this -   Col1    Col2                 abc     2016/05/23 abc     2016/08/13 abc     2016/11/29 abc     2017/02/15 pqr     2016/04/16 pqr     2017/01/27   The code I used is -   Data File2; Set File1; By col1; Lag_col2 = lag(col2); Dif_col2 = dif(col2); If first.col1 then do;   lag_col2 = .;   dif_col2 = .; End; Run;     The final answerset looked like this -   Col1    Col2                  Lag_col2           Dif_col2 abc     2016/05/23        .                         . abc     2016/08/13        2016/05/23        82 abc     2016/11/29        2016/08/13        108 abc     2017/02/15        2016/11/29        78 pqr     2016/04/16         .                        . pqr     2017/01/27         2016/04/16       286   The column Dif_Col2 gives me the difference between the dates for each id on col1.   Thanks again! ... View more