Could December 25 as the birthday of Jesus have come from Pagan influences?
It is doubtful since it is tradition that says otherwise.
We apply the name of Christmas to the forty days which begin with the Nativity of our Lord, December 25, and end with the Purification of the Blessed Virgin, February 2. It is a period which forms a distinct portion of the Liturgical Year, as distinct, by its own special spirit, from every other, as are Advent, Lent, Easter, or Pentecost. One same Mystery is celebrated and kept in view during the whole forty days. Neither the Feasts of the Saints, which so abound during this Season; nor the time of Septuagesima, with its mournful Purple, which often begins before Christmastide is over, seem able to distract our Holy Mother the Church from the immense joy of which she received the good tidings from the Angels [St Luke ii 10] on that glorious Night for which the world had been longing four thousand years. The Faithful will remember that the Liturgy commemorates this long expectation by the four penitential weeks of Advent.
But it was not till the fourth century that the Churches of the East began to keep the Feast of our Saviour’s Birth in the month of December. Up to that period they had kept it at one time on the sixth of January, thus uniting it, under the generic term of Epiphany, with the Manifestation of our Saviour made to the Magi, and in them to the Gentiles; at another time, as Clement of Alexandria tells us, they kept it on the 25th of the month Pachon (May 15), or on the 25th of the month Pharmuth (April 20). St John Chrysostom, in the Homily we have just cited, which he gave in 386, tells us that the Roman custom of celebrating the Birth of our Saviour on December 25 had then only been observed ten years in the Church of Antioch. It is probable that this change had been introduced in obedience to the wishes of the Apostolic See, wishes which received additional weight by the edict of the Emperors Theodosius and Valentinian, which appeared towards the close of the fourth century, and decreed that the Nativity and Epiphany of our Lord should be made two distinct Festivals. The only Church that has maintained the custom of celebrating the two mysteries on January 6 is that of Armenia; owing, no doubt, to the circumstance of that country not being under the authority of the Emperors; as also because it was withdrawn at an early period from the influence of Rome by schism and heresy. - The History of Christmas (Dom Guéranger)
But what are its' origins as a feast?
Concerning the date of Christ's birth the Gospels give no help; upon their data contradictory arguments are based. The census would have been impossible in winter: a whole population could not then be put in motion. Again, in winter it must have been; then only field labour was suspended. But Rome was not thus considerate. Authorities moreover differ as to whether shepherds could or would keep flocks exposed during the nights of the rainy season.
Zachary's temple service
Arguments based on Zachary's temple ministry are unreliable, though the calculations of antiquity (see above) have been revived in yet more complicated form, e.g. by Friedlieb (Leben J. Christi des Erlösers, Münster, 1887, p. 312). The twenty-four classes of Jewish priests, it is urged, served each a week in the Temple; Zachary was in the eighth class, Abia. The Temple was destroyed 9 Ab, A.D. 70; late rabbinical tradition says that class 1, Jojarib, was then serving. From these untrustworthy data, assuming that Christ was born A.U.C. 749, and that never in seventy turbulent years the weekly succession failed, it is calculated that the eighth class was serving 2-9 October, A.U.C. 748, whence Christ's conception falls in March, and birth presumably in December. Kellner (op. cit., pp. 106, 107) shows how hopeless is the calculation of Zachary's week from any point before or after it.
Analogy to Old Testament festivals
It seems impossible, on analogy of the relation of Passover and Pentecost to Easter and Whitsuntide, to connect the Nativity with the feast of Tabernacles, as did, e.g., Lightfoot (Horæ Hebr, et Talm., II, 32), arguing from Old Testament prophecy, e.g. Zacharias 14:16 sqq.; combining, too, the fact of Christ's death in Nisan with Daniel's prophecy of a three and one-half years' ministry (9:27), he puts the birth in Tisri, i.e. September. As undesirable is it to connect 25 December with the Eastern (December) feast of Dedication (Jos. Ant. Jud., XII, vii, 6).
The well-known solar feast, however, of Natalis Invicti, celebrated on 25 December, has a strong claim on the responsibility for our December date. For the history of the solar cult, its position in the Roman Empire, and syncretism with Mithraism, see Cumont's epoch-making "Textes et Monuments" etc., I, ii, 4, 6, p. 355. Mommsen (Corpus Inscriptionum Latinarum, 12, p. 338) has collected the evidence for the feast, which reached its climax of popularity under Aurelian in 274. Filippo del Torre in 1700 first saw its importance; it is marked, as has been said, without addition in Philocalus' Calendar. It would be impossible here even to outline the history of solar symbolism and language as applied to God, the Messiah, and Christ in Jewish or Christian canonical, patristic, or devotional works. Hymns and Christmas offices abound in instances; the texts are well arranged by Cumont (op. cit., addit. Note C, p. 355).
The earliest rapprochement of the births of Christ and the sun is in Cyprian, "De pasch. Comp.", xix, "O quam præclare providentia ut illo die quo natus est Sol . . . nasceretur Christus." — "O, how wonderfully acted Providence that on that day on which that Sun was born . . . Christ should be born."
In the fourth century, Chrysostom, "del Solst. Et Æquin." (II, p. 118, ed. 1588), says: "Sed et dominus noster nascitur mense decembris . . . VIII Kal. Ian. . . . Sed et Invicti Natalem appelant. Quis utique tam invictus nisi dominus noster? . . . Vel quod dicant Solis esse natalem, ipse est Sol iustitiæ." — "But Our Lord, too, is born in the month of December . . . the eight before the calends of January [25 December] . . ., But they call it the 'Birthday of the Unconquered'. Who indeed is so unconquered as Our Lord . . .? Or, if they say that it is the birthday of the Sun, He is the Sun of Justice."
Already Tertullian (Apol., 16; cf. Ad. Nat., I, 13; Orig. c. Cels., VIII, 67, etc) had to assert that Sol was not the Christians' God; Augustine (Tract xxxiv, in Joan. In P.L., XXXV, 1652) denounces the heretical identification of Christ with Sol.
Pope Leo I (Serm. xxxvii in nat. dom., VII, 4; xxii, II, 6 in P.L., LIV, 218 and 198) bitterly reproves solar survivals — Christians, on the very doorstep of the Apostles' basilica, turn to adore the rising sun. Sun-worship has bequeathed features to modern popular worship in Armenia, where Christians had once temporarily and externally conformed to the cult of the material sun (Cumont, op. cit., p. 356).
But even should a deliberate and legitimate "baptism" of a pagan feast be seen here no more than the transference of the date need be supposed. The "mountain-birth" of Mithra and Christ's in the "grotto" have nothing in common: Mithra's adoring shepherds (Cumont, op. cit., I, ii, 4, p. 304 sqq.) are rather borrowed from Christian sources than vice versa.
Other theories of pagan origin
The origin of Christmas should not be sought in the Saturnalia (1-23 December) nor even in the midnight holy birth at Eleusis (see J.E. Harrison, Prolegom., p. 549) with its probable connection through Phrygia with the Naasene heretics, or even with the Alexandrian ceremony quoted above; nor yet in rites analogous to the midwinter cult at Delphi of the cradled Dionysus, with his revocation from the sea to a new birth (Harrison, op. cit., 402 sqq.).
The astronomical theory
Duchesne (Les origines du culte chrétien, Paris, 1902, 262 sqq.) advances the "astronomical" theory that, given 25 March as Christ's death-day [historically impossible, but a tradition old as Tertullian (Adv. Jud., 8)], the popular instinct, demanding an exact number of years in a Divine life, would place His conception on the same date, His birth 25 December. This theory is best supported by the fact that certain Montanists (Sozomen, Church History VII.18) kept Easter on 6 April; both 25 December and 6 January are thus simultaneously explained. The reckoning, moreover, is wholly in keeping with the arguments based on number and astronomy and "convenience", then so popular. Unfortunately, there is no contemporary evidence for the celebration in the fourth century of Christ's conception on 25 March.
The present writer in inclined to think that, be the origin of the feast in East or West, and though the abundance of analogous midwinter festivals may indefinitely have helped the choice of the December date, the same instinct which set Natalis Invicti at the winter solstice will have sufficed, apart from deliberate adaptation or curious calculation, to set the Christian feast there too. - Christmas (Catholic Encyclopedia)
In 2000, Joseph Cardinal Ratzinger (future Pope Benedict XVI) wrote in his book The Spirit of the Liturgy has some key incites into our subject at hand. If the annunciation was on the 25th of March, then it stands to reason Christ was born nine months later, December 25.
In 2000, Joseph Cardinal Ratzinger wrote in his book The Spirit of the Liturgy that a Jewish tradition holds that Abraham almost sacrificed Isaac on Mount Moriah on March 25. Mount Moriah is Jerusalem (see 2 Chron 34:1), and March 25 is the date on which Christ was crucified on the solar calendar (Easter like the Mosaic Passover is calculated by a lunar phenomenon). I think that you can see that there is a geographical and temporal parallel here. We see that the Father willingly offers His only-begotten Son.
Cardinal Ratzinger also noted that March 25 was thought to be the first day of creation. Hence, March 25 has a cosmic significance. His Eminence also describes how the zodiac and Aries relates to this cosmic significance in the Spring, but that is a bit too much for our purposes. The important thing is that March 25 was the traditional date for the creation of the world, for the sacrifice of Abraham, and for the sacrifice of God the Son.
On pages 107-108, Cardinal Ratzinger makes the observation that the day of Christ’s death was also reckoned as the day he was conceived by the Holy Ghost in the womb of the Blessed Virgin Mary. March 25, then was the annunciation of Gabriel. Add nine months to that and you arrive at December 25 as His birthday.
Ratzinger then dismisses what he calls “these old theories” that teach that December 25 was chosen to cover over pagan holidays. Rather, the Holy Father recognizes December 25 as the true birthday of Christ the Lord. He expands that this alignment of meanings has liturgical significance.
While we’re on the topic, Pope Saint Leo the Great spoke of the cosmic meaning of Christ’s birth in the depth of winter:
"But this Nativity which is to be adored in heaven and on earth is suggested to us by no day more than this when, with the early light still shedding its rays on nature, there is borne in upon our senses the brightness of this wondrous mystery." (St Leo Magnus, Sermo 26)
Also, Pope Benedict XIV argued that the church fathers would have known the correct date of birth from Roman census records. - Pope Benedict XVI: December 25 as the Historical Date of the Christ’s Birth
Although Christmas does not appear on the lists of festivals given by the early Christian writers Irenaeus and Tertullian. Origen and Arnobius both fault the pagans for celebrating birthdays, which suggests that Christmas was not celebrated in their time. Arnobius wrote after AD 297. The Chronography of 354 records that a Christmas celebration took place in Rome in 336.
Nimrod could not be of any influence on the date of Christmas, for one thing we do not know the exact year of his birth or death. To top it off, the Babylonian calendar was a lunisolar calendar with years consisting of 12 lunar months, each beginning when a new crescent moon was first sighted low on the western horizon at sunset, plus an intercalary month inserted as needed by decree. The calendar is based on a Sumerian (Third Dynasty of Ur) predecessor preserved in the Umma calendar of Shulgi (c. 21st century BC). This means that festivals varied in date from year to year, just as the ancient Jewish calendar did.
The website of the Church of Satan has no historical bases for any of their claims.
As for myself, I believe that it is possible that the winter solstice may have had a greater influence in the decision of the date of December 25th, than we may realize.
Since the Julian calendar looses about three days every four centuries, it is not impossible that the actual birth of Christ could have been on the actual winter solstice (December 21/22) and St. John’s birth could have been on the summer solstice (June 20-23). Of course this is only a side note in making this a more liturgical symbolic statement of St. John in his Gospel: “He must increase, but I must decrease!” - St. John Baptist (John 3:30)
Winter & Summer Solstices are symbols for Christ and St. John the Baptist respectfully. The summer solstice is another symbolic date in the medieval Catholic world. The summer solstice, also called St. John's Eve, occurs on June 21, the longest day of the year, presaging the birth of St. John the Baptist on June 24. This has significance, for St. John Baptist was understood to be preparing the way for Christ, with St. John (3:30) stating: "He must increase, but I must decrease." This declaration is symbolized in the fact that the sun begins to diminish at the summer solstice. On the contrary at the winter solstice, the sun begins to increase.