Old file requires newer version?

[Carpetnailz]

I've got an old GnuCash file from a few years ago that I'm trying to
open. It seems to be in XML format. When I try to open it I get the
strange error message that

"The file/URL appears to be from a newer version of GnuCash. You must
upgrade your version of GnuCash to work with this date."

I get the same error when I try to open an .xac file that has a date of
2009 on it.

I don't understand why an older file would require a newer version of
GnuCash. I'm now running 2.4.11, which seems to be the current version.

Thanks.