why does the ENTIRE world subscribe to the Christian calendear?
Because in what we nor refer to as 310 AD (or CE) Constantine made Christianity the official religion of the Roman Empire. the sixth century a monk named Dionysius incorrectly placed the birth of Christ at the end of 1 BC (although the term BC wasn't used at the time). The counting system was eventually adopted by the church, and by extension the Western world. (A common system of dating became extremely important as people travelled more.) Non-Christian countries began using it for convenience.
There's more to it than that, but that's the general gist.
We may use the date of the birth of Jesus for our year, but we use other gods and historical figures for our days and months. Is that significant as anything other than a historical accident?
Thanks for playing into my hand.
Whatever. You probably foresaw this rebuttal too, let me know when you get to the point.
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"Theology is never any help; it is searching in a dark cellar at midnight for a black cat that isn't there. Theologians can persuade themselves of anything." -Robert A. Heinlein