b.c. and counting

a dozen years before Christ
what year did everyone think it was?
they didn't walk around saying it's twelve before zero
and they must have had a New Years
so what year did they celebrate?

in five b.c. if you told someone you'd pay them the money you owed in four b.c.
they'd squint, scratch, then club your head

what did they do when they had to fill out an official form
and write down the year of birth?
"you wrote you were born in minus 36
how did you figure that?
that'll cost you three shiny stones and a chunk of obsidian for being a wise ass"