
The DATEDIF function can be used to calculate the number of days/moths/years between two dates in versions of Excel from 97 to 2007.
=DATEDIF(B9,C9,"m")/12
=DATEDIF(B9,TODAY(),"d")
=DATEDIF(B9,C9,"m")
It is interesting to note that DATEDIF is not listed with other functions under the formula tab in Excel 2007.