SAS stores dates internally as the number of days from 1/1/1960, so date arithmetic is simple. If effective_date is a SAS date, then expr_dt = effective_date-1; FORMAT expr_dt date9.; should do it. If effective_date is a character string, then you need to first convert it to a SAS date using the INPUT function, like effective_date_new= INPUT(effective_date, anydate9.); Doc Muhlbaier Duke
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