I would like to subtract the second IncarcerationDate minus the first ReleaseDate based on ID. For example there is an ID with the number 1 with eight different start dates and end dates, Id 2 has one record, id 3 has four records. I would like a new variable "DaysAtHome", substract first.id ReleaseDate from second.id IncarcerationDate and for last record (last.id) susbtract from SysDate(Today's Date) -ReleaseDate. Any help would be greatly appreciated. Thanks.    Here is a dataset: data incarceration; input Id $ IncarcerationDate :mmddyy10. ReleaseDate :mmddyy10.; format IncarcerationDate ReleaseDate mmddyy10.; datalines; 1 08/12/2019 08/13/2019 1 08/20/2019 10/02/2019 1 10/31/2019 11/01/2019 1 11/07/2019 11/08/2019 1 11/29/2019 01/02/2020 1 01/15/2020 03/25/2020 1 08/05/2020 08/08/2020 1 10/21/2020 01/07/2021 2 01/21/2018 01/23/2018 3 11/07/2018 01/07/2019 3 04/25/2018 05/09/2018 3 08/14/2020 08/17/2020 3 03/22/2018 04/11/2018 ; run;   I want a new Variable "DaysAtHome": Id IncarcerationDate ReleaseDate DaysAtHome   1 8/12/2019 8/13/2019 7 8/20/2019 - 8/13/2019 1 8/20/2019 10/2/2019 29 10/31/2019 - 10/02/2019 1 10/31/2019 11/1/2019 6   1 11/7/2019 11/8/2019 21   1 11/29/2019 1/2/2020 13   1 1/15/2020 3/25/2020 133   1 8/5/2020 8/8/2020 74   1 10/21/2020 1/7/2021 1317 today's date -01/07/2021 2 1/21/2018 1/23/2018 2397 today's date -01/23/2018 3 3/22/2018 4/11/2018 14   3 4/25/2018 5/9/2018 182   3 11/7/2018 1/7/2019 585   3 8/14/2020 8/17/2020 1460     Wrote few codes but did not get the results. proc sort data=incarceration; by Id IncarcerationDate; run;   data days_home; set incarceration; by Id; SysDate = today();   prevReleaseDate=lag(ReleaseDate); if not last.id then DaysAtHome=IncarcerationDate-prevReleaseDate; if last.Id then DaysAtHome = SysDate - ReleaseDate; run; ... View more