We can always use this:

trust those italians to screw it all up

Unless you're Jewish and celebrate their calendar and celebrate in September.

Actually, we are supposedly counting days since the Birth of Christ, not the crucifixion.

[en.wikipedia.org]

So he would have presumably been crucified in 33 AD. However, apparently most Biblical scholars now put the date of Christ's birth between 6 BC and 4 BC. That is, off course, assuming that such a person actually existed.

Probably so simply because nearly the entire planet uses the same calendar now. But we no longer use A.D. and B.C. (which both are Christian terms) when referring to years anymore. It seems C.E. (current era) and B.C.E. (before current era) have replaced them. So, that's some progress.

there are other calenders

Maybe when we start traveling through space? The scifi geek in me can hope.

The historical Jesus (Joshua) was born sometime around 6 BC and died at the age of 33 or 35, but none of this can definitely be certain. What we most 'know' about is the religious fantasy Jesus.

I think it might change one day? What about this?

IT'S THE YEAR 7 000 018
This is for those who take the start point from where evolution turned to create humans. Scientists say that it was about 7000000 years ago? Start of the human lineage, following a split with the lineage containing chimpanzees and gorillas.