[@Landaus Five-One]  All I know is it's about 5000 years since the downfall of humanity.  We don't know when that occurred.  I'm in favor of the demons coming up with a different year system than the Christian one, because I figure they'd see that as an arbitrary date.  Actually, we don't even know if this world has Christianity, since we have proof of multiple gods, so that'd make using the Christian calendar strange to begin with.