How to utilize date add function in Google spreadsheet?

Question

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

Answer 1

what's wrong with simple add and convert back?

if A1 is a date field, and A2 hold the number of days to add: =TO_DATE((DATEVALUE(A1)+A2)