DATEDIF calculates a month off

Suppose my start and end dates are in A1 & A2 respectively and I want
to count the number of months between them

A1: 09/01/04
A2: 01/31/05

=DATEDIF(A1,A2,"M") returns 4, instead of the correct count of 5.

What's up with that?

Anybody?

Thanks.
M&M

DATEDIF(...,"m") counts only whole months, presuming that days start at
midnight. So your span is only 4 months and 30 days long, not 5 months.

Of course, the whole concept of months is rather squirrelly. For
instance, one month after 1/30/05 - is it 2/28/05 (29 days), 3/1/05 (30
days)?, 3/2/05 (31 days)?

In article <[email protected]>,
"Mary" <[email protected]> wrote:

> Suppose my start and end dates are in A1 & A2 respectively and I want
> to count the number of months between them
>
> A1: 09/01/04
> A2: 01/31/05
>
> =DATEDIF(A1,A2,"M") returns 4, instead of the correct count of 5.
>
> What's up with that?