Celtic, thankyou very much.

Maybe the Romans did too, but they don't matter (bloody foreigners). Besides, they were degenerate.

And, yes, it would make more sense in a way, but, no.

The numbers wouldn't make sense any more - 60 seconds in a minute, 60 minutes in an hour, 2x12 hours in a day, 13 months in a year ... wait, what?

Furthermore, if we had thirteen months, we wouldn't get a five week bonus every four years and I'd have to recalculate it all ... and I'm not doing that, so, no.- away with you, you Portuguese FREAK!