I personally number the years since the so-called "Big Bang" and the creation of the Universe. I call those years "ABB". I don't know anything about BBB.

We learned about the possible revised date of the birth of Yeshua of Nazareth back in high school. Benny 16 didn't say anything new there. Of course, the chances are excellent that the birth was in the Spring -- April or May -- as well. The early Christians were adept at transforming things like the Saturnalia. And look what they did to poor Bridget in Ireland!