=DATEDIF – If you ever need to determine the number of months between two dates, the simplest way is with the =DATEDIF function. Here's a sample scenario: =DATEDIF(A1,B1,”m”) will return 12 if cell A1 contains the date 01/01/02 and cell B1 contains the date 12/31/02. If this is a function you can use, make sure to make a note of it in a place where you'll remember, because it's only documented in Excel 2000! You won't find mention of it in any other Excel version. Chip Pearson offers some additional background on this function, including its storied history.