In The Infancy Narratives: Jesus of Nazareth Pope Benedict makes a strong case for the star which led "the Magi", really, to Jerusalem and to Bethlehem. The Magi were members of the Persian priesthood and probably with some connection with the scientific research in Babylon which had previously had a center of scientific astronomy. And it is certain that there was a peculiar conjunction of the planets Jupiter and Saturn in the constellation Pisces in the years 7-6 B.C.--now believed to be the actual time of Jesus' birth--which the Babylonian astronomers were quite capable of calculating..."and it may well have pointed them toward the land of Judea and to a newborn "'king of the Jews.'" p. 94 ff.
Having finished the last published volume of the Jesus of Nazareth trilogy I have to say that this last volume is the least satisfying, though, for that, it is filled with insights and the present state of theological and historical knowledge on a number of Incarnation events. One thing the Holy Father could have mentioned and did not is the dates of Christmas, Epiphany and the chronology of the arrival of the Magi in relation to the birth. When did the Magi come in relation to the birth of Christ and the Presentation, for instance? It seems to me that this volume was rushed to the press without being properly finished. Perhaps the Holy Father might consider making a fuller volume, a full volume one, on the Infancy Narratives and the hidden life of Jesus.
Here is an attempt at an explanation which I found regarding the possible historical origins of the 25th of December as the date for Christmas (besides the obvious answer that it could have been the actual day of the birth of Christ; although we all know that there are twelve days of Christmas anyway).
The key to dating Jesus’ birth may lie in the dating of Jesus’ death at Passover. This view was first suggested to the modern world by French scholar Louis Duchesne in the early 20th century and fully developed by American Thomas Talley in more recent years.8 But they were certainly not the first to note a connection between the traditional date of Jesus’ death and his birth.
The baby Jesus flies down from heaven on the back of a cross, in this detail from Master Bertram’s 14th-century Annunciation scene. Jesus’ conception carried with it the promise of salvation through his death. It may be no coincidence, then, that the early church celebrated Jesus’ conception and death on the same calendar day: March 25, exactly nine months before December 25. Kunsthalle, Hamburg/Bridgeman Art Library, NY
Around 200 C.E. Tertullian of Carthage reported the calculation that the 14th of Nisan (the day of the crucifixion according to the Gospel of John) in the year Jesus diedc was equivalent to March 25 in the Roman (solar) calendar.9 March 25 is, of course, nine months before December 25; it was later recognized as the Feast of the Annunciation—the commemoration of Jesus’ conception.10 Thus, Jesus was believed to have been conceived and crucified on the same day of the year. Exactly nine months later, Jesus was born, on December 25.d
This idea appears in an anonymous Christian treatise titled On Solstices and Equinoxes, which appears to come from fourth-century North Africa. The treatise states: “Therefore our Lord was conceived on the eighth of the kalends of April in the month of March [March 25], which is the day of the passion of the Lord and of his conception. For on that day he was conceived on the same he suffered.”11 Based on this, the treatise dates Jesus’ birth to the winter solstice.
Augustine, too, was familiar with this association. In On the Trinity (c. 399–419) he writes: “For he [Jesus] is believed to have been conceived on the 25th of March, upon which day also he suffered; so the womb of the Virgin, in which he was conceived, where no one of mortals was begotten, corresponds to the new grave in which he was buried, wherein was never man laid, neither before him nor since. But he was born, according to tradition, upon December the 25th.”12
In the East, too, the dates of Jesus’ conception and death were linked. But instead of working from the 14th of Nisan in the Hebrew calendar, the easterners used the 14th of the first spring month (Artemisios) in their local Greek calendar—April 6 to us. April 6 is, of course, exactly nine months before January 6—the eastern date for Christmas. In the East, too, we have evidence that April was associated with Jesus’ conception and crucifixion. Bishop Epiphanius of Salamis writes that on April 6, “The lamb was shut up in the spotless womb of the holy virgin, he who took away and takes away in perpetual sacrifice the sins of the world.”13 Even today, the Armenian Church celebrates the Annunciation in early April (on the 7th, not the 6th) and Christmas on January 6.e
Thus, we have Christians in two parts of the world calculating Jesus’ birth on the basis that his death and conception took place on the same day (March 25 or April 6) and coming up with two close but different results (December 25 and January 6).
Connecting Jesus’ conception and death in this way will certainly seem odd to modern readers, but it reflects ancient and medieval understandings of the whole of salvation being bound up together. One of the most poignant expressions of this belief is found in Christian art. In numerous paintings of the angel’s Annunciation to Mary—the moment of Jesus’ conception—the baby Jesus is shown gliding down from heaven on or with a small cross (see photo above of detail from Master Bertram’s Annunciation scene); a visual reminder that the conception brings the promise of salvation through Jesus’ death.
The notion that creation and redemption should occur at the same time of year is also reflected in ancient Jewish tradition, recorded in the Talmud. The Babylonian Talmud preserves a dispute between two early-second-century C.E. rabbis who share this view, but disagree on the date: Rabbi Eliezer states: “In Nisan the world was created; in Nisan the Patriarchs were born; on Passover Isaac was born … and in Nisan they [our ancestors] will be redeemed in time to come.” (The other rabbi, Joshua, dates these same events to the following month, Tishri.)14 Thus, the dates of Christmas and Epiphany may well have resulted from Christian theological reflection on such chronologies: Jesus would have been conceived on the same date he died, and born nine months later.15
It is quite remarkable that the whole world celebrates the date of the Lord's birth completely based on the Tradition of the Church, whether it is the 6th of January of the 25th of December, actually we all celebrate the entire twelve days as if one day! The marvel is that here is a central Christian celebration in the modern world which was determined by the Popes (along with the solar calendar which we follow and the numbering of the years with the Incarnation as the focal point).