Two reasons, actually. First and foremost, I wanted a calendar for a game that didn't get into the excessively high numbers when in a hypothetical interstellar-colonisation-era -- something about 3000 AD just grates on me. Secondly, in that game, the separation between church and state became extremely strong to the point that all directly-religious aspects of society were removed. People are free to exercise their religious beliefs in that future, but they're not allowed to break the ethics of the land in so doing (in other words, if your religion says "we have to sacrifice an infidel every second Tuesday", the government will say, "killing people is illegal, so you are not allowed to exercise that aspect of your religious belief, or else"). This caused a few splinter factions of religious nuts and insurgents (remembering that this is interstellar-era, so there's lots of room for these people to find places to hide from the law), but for the most part everyone is happy with it.

The New Calendar showcases what I believe to be the critical stage of human development, when humanity truly began to develop culturally and technologically. The Renaissance, the Middle Ages, the Dark Ages... all of them were foundational, but none of them truly and critically established the modern sentiment of individuality and freedom that the Industrial Revolution did, nor did any of them eliminate the rich-poor division as much as the Industrial Revolution did. There are still plenty of rich people and there are still plenty of poor people in modern times (I'm one of the latter), but even poor people can afford cars, internet access, and all the food they want as long as they actually get off their butts and work once in a while. (This is all taken from the stance of our industrialised nations. I'm well aware of the plights of developing nations and feel very sorry for them. I sometimes wish I could do more than just make some random donation to some religious charity where only a fraction of the profits actually go directly to the people I want to help.)

Besides all that, it just looks neat! It's got the whole Star Trek numeric feel without being quite as pointless as the Star Trek numeric feel.

I assume your game involves more species than humans, than? Because I really don't see humans separating religion from government anytime soon. Indeed, their goals are so similar (IE power and control) that they often naturally entwine (governments claiming divine authority and religions claiming sole government sanction, for example). And belief is intrinsic to human behavior, whether it be religious or not.

Anyway, better stop now before I start babbling about machine gods and techno-priests....