The Excel function: TODAY
Returns the serial number of the current date. The serial number is the date-time code used by Excel for date and time calculations. If the cell format was General before the function was entered, Excel changes the cell format to Date. If you want to view the serial number, you must change the cell format to General or Number.
The TODAY function is useful when you need to have the current date displayed on a worksheet, regardless of when you open the workbook. It is also useful for calculating intervals. For example, if you know that someone was born in 1963, you might use the following formula to find that person's age as of this year's birthday:
This formula uses the TODAY function as an argument for the YEAR function to obtain the current year, and then subtracts 1963, returning the person's age.
Note If the TODAY function does not update the date when you expect it to, you might need to change the settings that control when the workbook or worksheet recalculates. On the File tab, click Options, and then in the Formulas category under Calculation options, make sure that Automatic is selected.