Linus' reply is a bit terse. The intnx function will provide an answer, provided you supply the right question. Do you want 9 calendar months exactly (ie to the same day - if possible - 9 months previously), or do you just need the month and the first day will do; or maybe push all dates back by the same amount (0.75 year = 274 days)? Taking these options in reverse order: Prev_date = date - 274 ; Prev_date = intnx("MONTH", date, -9) ; Prev_date = intnx("MONTH", date, -9, "SAME") ; INTNX is documented here SAS(R) 9.2 Language Reference: Dictionary, Fourth Edition BTW, if your dates are datetime intervals you need to use "DTMONTH" instead of "MONTH" ; and for the 274 day calculations use Prev_date = intnx("DTDAY", date, -274, "SAME") ; Richard
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