adding dates

From: Anthony Hosking (mrmclarge_at_yahoo.co.uk)
Date: 05/26/04 

Date: Wed, 26 May 2004 21:48:07 +1200

if I have todays date, and I want to add 7 days to it, so that the
date then will be 7 days ahead, How do I do that

I do not want to change the date, just get a new one so that I can
test to see if the new date has been reached.

Many thanks