Question: Where did our Gregorian calendar come from?
Reply: Our secular calendar has a long history. Originally the first month was March, so that the seventh month was September (septem = 7), and the 10th was December (decem = 10). "The opening of the year was moved from 1 March to 1 January, probably in 153 B.C" (J.B. Segal, The Hebrew Passover, London: Oxford UP, 1963, p. 121). Of course, it wasn't "B.C." back then, it was "AUC" - "years from the founding of the city of Rome." It stayed "AUC" until the Western Roman Empire was overthrown. So Pope John I asked a monk named Dionysius Exiguus to figure out how many years it had been since the birth of Jesus. He said 531 years, so the Pope announced that the next year would be called 532 A.D. (Anno Domini = Year of the Lord). It is now generally thought that Jesus was born 4 B.C. So B.C. now stands for "Before the Christian Era = B.C.E.", not "Before the birth of Christ". There was no year zero, so we count the years as 4 B.C., 3 B.C., 2 B.C., 1 B.C., 1 A.D., 2 A.D..... This is the year 1999 A.D., so it is 2002 years since the birth of Jesus. There was another little miscalculation which meant that each year was a bit too long. A change of a few days was initiated by Pope Gregory XIII in the 1500s. The standard secular calendar is now the Gregorian calendar. About 7,000 A.D. our calendar will be 1 day incorrect and will need further correction. The Muslim world uses a different calendar based only on the moon.

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