@davies wrote: Hi,   Thanks all for the quick replies! As luck would have it, just after I posted this I adapted this code to account for dates: https://communities.sas.com/t5/Statistical-Procedures/How-to-split-record-into-multiple-rows-one-row-per-month-year/td-p/249306   In the end, I did this, but your way seems much more efficient, I'll try that!    Thanks again!    data want;    set have;   date=StartDate;   if StartDate lt EndDate then do while (date lt EndDate);    day=day(date);    month=month(date);    year=year(date);    output;   date=intnx('day',date,1);   end;   drop date;  run; Behavior difference at beginning of the interval if the start = end. With the DO loop the it will execute once. The DO WHILE as shown would not execute. I would guess the above code was written by someone either less familiar with SAS DO loop construct using start and end variable values or from a programming language/school that does everything with DO WHILE/UNTIL and not iterated loops for some other reason.. ... View more