In another cell use the DATEDIF formula with the ym parameter. DATE 2015 5 20 - returns a serial number corresponding to 20-May-2015. With reference to the sample workbook.
Here are a few Excel DATE formula examples.
2In the Date Time Helper dialog box please do the following operations. To get a future date which is 100 days later based on current date please apply the following simple formula. Date function will take the input from the user for a date month and year they will give results in the serial number or date format. Select the Formulas Tab then Date Time.