Add 12 weeks -- or any number of weeks -- to dates in Excel by using a formula to add the corresponding number of days.
Insert a new column designed to hold the new dates and select the cell where the first new date should appear. Click the fx icon to open the Function Arguments window.
Under certain circumstances, Excel may place an equal sign before a date, thereby indicating that it treats the date as a division operation rather than an actual date. Rectify this issue before proceeding with adding days to the date by assigning the correct format to the cell that holds it. To do so, click the cell, open the Format drop-down menu and select Date from it.
Select Sum from the list of available functions and click the OK button.
Place your cursor in the Number1 field and select the first date from the spreadsheet.
Enter the number of days you want to add to the date in the Number2 field and click the OK button. For example, to add 12 weeks to a date, enter 84 (12 multiplied by 7).
- As an alternative to using the function wizard, enter =CellNumber+NumberofDays in a new cell to add days to an existing date. For example, typing a =B2+84 formula would add 84 days -- or 12 weeks -- to a date located in B2.
- Add months to a date by entering the =EDATE(CellNumber,NumberofMonths) formula -- where CellNumber is the number of the cell that holds the original date and NumberofMonths the number of months you wish to add to it -- in a new cell.
Apply the same formula to multiple dates, if needed, by clicking the square icon -- also known as the fill handle -- that appears at the bottom-right corner of the cell that holds the formula you just created and dragging it to other cells.