Just use the Date function, as in:
=Date(year(a1),month(a1)-9,day(a1))

Regards,
Fred

"sonia" wrote in message
...
Hi

is there a way to figure out a date 9 months previous to a date?

eg. I have an install date of 12/02/10, is there a way or a formula that
can
count back 9 months from that install date? (they need to be weekdays)

thanks very much