It is simple all you need to do is use Date2Num and Num2Date inbuilt functions.... Here is what I have tried....
I used a table with 7rows and in the 2nd column I used Date/Time Field in each one of those. I named one after another as week1sunday, week1monday....
then except the fist one (week1sunday) rest of the ones I made readOnly. Now in the change event of week1sunday I used the following code to produce the calculating effect....this is FormCalc code
$.parent.parent.Row2.week1monday.rawValue = Num2Date(Date2Num(xfa.event.change,"M/D/YY")+1,"M/D/YY")
$.parent.parent.Row3.week1tuesday.rawValue = Num2Date(Date2Num(xfa.event.change,"M/D/YY")+2,"M/D/YY")
Of course you need to match with your SOM hierarchy but you can use the concepts.
Good luck,