My mistake I misread the OP post

Thanks for pointing it out

"Ron Rosenfeld" wrote:

On Sun, 7 Oct 2007 18:46:00 -0700, Mike wrote:

Try this
=DATE(YEAR(A1),MONTH(A1)+3,1)

Did you try this solution?

Aside from the fact that the OP changed his original request from 3 months to
90 days, your solution rounds down and doesn't work on the example the OP gave.

--ron