Try this:

=EDATE(A1,-20)

Required Analysis ToolPak Add-Ins



"Rob" wrote:

Given a base date such as 10/1/2006, how do you return a date knowing the
number of months previous to the base date? Using this for a project plan
and want to return the value for A-20 where A is the base date and 20 is the
number of months before the base date.
Thanks for your help.