Why does the modulo function in excel return the divisor?

Question

I have an Excel validation formula which worked fine in Office '03, '07, but is failing in 2010. Did they change the definition of MOD recently?

In 03/07 the following returns zero:

=MOD(1, .05)

However in 2010 it returns .05.

As far as I can tell they haven't changed how remainders worked since I was in 3rd grade when I learned about them. However, Microsoft may be taking certain liberties.

Answer 1

So I finally decided the best way to determine this was to cheat and do:

=(1/.05)-(floor(1/.05))

That gives me the zero I need.

Answer 2

Actually... it does not return zero in Office 2007, but -0.000000000000000056 (just tested).

Maybe it's a floating point issue or the way Excel 2010 handles floating point changed.