Create a DATA step to produce a value for the function STUDY_DAY. The function uses a start date and today's date to compute the value. STUDY_DAY is called from the DATA step. When the DATA step encounters a call to STUDY_DAY, it does not find this function in its traditional library of functions. It searches each of the data sets that are specified in the CMPLIB system option for a package that contains STUDY_DAY. In this case, it finds STUDY_DAY in sasuser.funcs.trial.

data _null_;
   start = '15Feb2008'd;
   today = '27Mar2008'd;
   sd = study_day(start, today);