I believe the issue I am having now should be much easier in MS Excel. However, since my company uses Google Spreadsheet so I have to figure out a way.
Basically, I have
You can just add the number to the cell with the date.
so if A1: 12/3/2012 and A2: =A1+7 then A2 would display 12/10/2012
A1: 12/3/2012
A2: =A1+7