It would have been good to get out of the strictly western approach. The lunar calendar used in Asia (and it was used also uin other places) is still dictating festivals and new years in the Far East. The Mayas had a completely different way of counting days and years, in fact several concomitant ways. And the Maya Long Count is still present in some Amerindian cultures. And Islam has another way of using the count of years rooted in their faith. And there are still some more. What about the Greeks, the Babylonians, the Persians, the Indians from India, the Buddhists of various branches of Buddhism, and the Chinese, or Japanese? Not to mention Polynesians and Africans. The standard use of the Christian calendar in the world is in no way exclusive of other ways to count time. That's why Easter moves around, not to speak of Oriental new years and Islamic Ramadan. The only exception in your article is the Hebrew calendar which is not really an exception since Jesus was a Jew and there would be no Christian era if there had not been a Hebrew era before in the Middle East, in Palestine.