Little Hawk commented, inter alia:

The thing that determines our actual year is the relationship of the planet Earth to the Sun, its movements around the Sun, and Pope Gregory was, of course, aware of that when he decided to ratify the present calendar, but why make the year begin on January 1st?

Two comebacks to that:

Pope Gregory was NOT "of course" aware of that. It's quite possible (in my view, quite likely) that he believed that the sun went around the earth. After all, it hadn't been all that long since Leonardo was charged and convicted of heresy for denying that the sun went around the earth, and it wasn't until the 20th Century (!!!) that the Catholic Church admitted that the earth went around the sun.

But why did he set January 1st? Because Gregory was modifying Julius Caesar's system, what we call the Julian Calendar, which started the year on January 1st, and I suppose the Pope saw no particular reason to change the start point.

Now, why Julius Caesar used January 1st I don't know for sure, but he too was adjusting the system which existed in Rome from before his time.

But Little Hawk is correct in that there's nothing objectively "beginning-ish" about January 1st, other than "the way we've been used to thinking of it".

Dave Oesterreich