If you just put your cursor in A4 and enter formula =A3+7 press Enter. It will give you the date from A3 + 7 days (1 week). You can then AutoFill that DOWN the column as far as you like. Then AutoFill A4 across all the way to column G and repeat AutoFill down each column till all the cells are filled showing the dates you are after. From row 4 down you can AutoFill without issue both down columns and across rows.