Oh, this is cool.

If I paste the formula below into an Excel cell, I get 173.

When I try and look up DateDif in excel Help, it doesn't exist.

If '9' is the right answer, and SP2 gives 122, what the heck do I have?

I'm really glad it's Friday.

In the main SP2 fixes and improves things. However here's an odd bug which,
in limited testing, appears to have been introduced in SP2

=DATEDIF(DATE(2009,6,27),DATE(2012,1,5),"md")