ROME, 14 DEC 1999 (ZENIT)    With the Great Jubilee only days away, discussions are heating up about when the Third Millennium actually begins. While it is certain that Jubilee celebrations will start with the opening of the Holy Door on December 24 and end with its closing on January 6, 2000, it is less clear whether this is really the 2000^th anniversary of Christ's birth.

When Dionysius Exiguus computed the date of Christ's birth in the Middle Ages, he named the year of the Nativity 1 A.D., and stated that Jesus' birthdate was December 25 of that year. The year immediately before this was the year 1 B.C. Whether from mathematical ignorance or design, he did not include a year zero.

This complicates the calculation of the dates of the Jubilee. Christmas of the year 2 A.D. was the 1^st anniversary of Christ's birth, according to Dionysius' calculations; similarly, the second anniversary of that birth fell in the year 3 A.D. Taking this forward a few centuries, we find that the 2000^th anniversary of Christ's birth should fall on December 25, 2001.

To complicate matters further, it seems that Dionysius' made an error in his calculations. Herod the Great, who the Bible says was alive at the time of Christ's birth, died in the year 4 B.C., based on the reports of Josephus. According to the Gospel of Matthew, when Herod was unable to trick the astrologers into leading him to the Child, he ordered the slaughter of all the male babies in Bethlehem. Since Herod's command (which is not attested outside the Gospels, but is consistent with his historical character) was to kill all babies under age 2, this event occurred no more than 2 years after Christ's birth. If we assume that this happened near the end of Herod's life (which seems likely), this puts Christ's birth in the year 5 or 6 B.C.

In that case, the 2000^th anniversary of Christ's birth has already gone by, having been in 1993 or 1994. Naturally at the distance of years, it is practically impossibile to say with certainty what year Christ was actually born, though sometime between 7 B.C. and 1 B.C. seems all but certain.

If this is the case, why is the Church celebrating the year 2000 with such solemnity? The answer is simple: because the world is celebrating this date. In his Apostolic Letter "Tertio Millennio Adveniente," the Holy Father wrote, "In view of this, the two thousand years which have passed since the Birth of Christ (prescinding from the question of its precise chronology) represent an extraordinarily great Jubilee, not only for Christians but indirectly for the whole of humanity, given the prominent role played by Christianity during these two millennia. It is significant that the calculation of the passing years begins almost everywhere with the year of Christ's coming into the world, which is thus the centre of the calendar most widely used today. Is this not another sign of the unparalleled effect of the Birth of Jesus of Nazareth on the history of mankind?"

For the Pope, the year 2000 is a sign of the centrality of Christianity in our society, hence it is cause for celebration and Jubilee.