The first date must be earlier than the second date. Try
=DATEDIF(A1,B1,"m")

See www.cpearson.com/excel/datedif.htm for more information.


--
Cordially,
Chip Pearson
Microsoft MVP - Excel
Pearson Software Consulting, LLC
www.cpearson.com


"JohnH" wrote in message
...
I'm using Excel 2000 and trying to use the datedif function.
I've formated 2
columns as date m/dd/yyyy and left the formula column general
I'm entering
dates
A1: 1/1/2002
B1: 1/1/2005

I'm entering the formula in C1
=datedif(b1,a1,"M")

I'm looking for the nmber of months between 2 dates

I get #NUM! for a result.

Thanks
John