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Add or Subtract dates in Excel

​Suppose you want to adjust a project's schedule date by adding two weeks to see what the new completion date will be, or you want to determine how long a single activity will take to complete in a list of project tasks. You can add or subtract a number of days to or from a date by using a simple formula, or you can use worksheet functions that are designed to work specifically with dates in Excel. 

Suppose that an account balance of yours is due on February 8, 2010. You want to transfer funds to your checking account so that those funds arrive 15 calendar days before that date. In addition, you know that your account has a 30 day billing cycle, and you want to determine when you should transfer funds for your March 2010 bill so that those funds are available 15 days before that date.
  1. In cell A1, type 2/8/10.
  2. In cell B1, type =A1-15.
  3. In cell C1, type =A1+30.
  4. In cell D1, type =C1-15.


Cells A1 and C1 show the due dates (2/08/10 and 3/10/10) for the February and March account balances, and cells B1 and D1 show the dates (1/24/10 and 2/23/10) by which you should transfer your funds for those due dates.