Could December 25 as the birthday of Jesus have come from Pagan influences?

TLDR: According to the Bible, there is no reason to believe Jesus' birthday was on December 25th.

Biblically, what do we know about the approximate time of year that Jesus was born?

And there were in the same country shepherds abiding in the field, keeping watch over their flock by night.

Luke 2:8

If Jesus was born in December 25th, it would be winter in the Northern Hemisphere. It is highly unlikely that shepherds would be out in the field with their sheep during a winter night as it would be way too cold. December temperatures in the Bethlehem area range from 47-57 Fahrenheit. Snow fall in not uncommon and cold rain is very common.

Though the December 25th date likely has pagan origins, as you pointed out, many Christians use this holiday as an opportunity to share the Great Gift that was given to the world by the Father. The long-awaited Savior, Jesus Christ, had finally come to save humanity from sin.

Could December 25 as the birthday of Jesus have come from Pagan influences?

Doubtful seeing that Tertullian calculated that Jesus was conceived on March 25th, thus making December 25th the date of his birth!

There is another way to account for the origins of Christmas on December 25: Strange as it may seem, 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. But they were certainly not the first to note a connection between the traditional date of Jesus’ death and his birth.

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 died was equivalent to March 25 in the Roman (solar) calendar. 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. 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.

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.” 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.” - How December 25 Became Christmas

It is doubtful since tradition also 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?

The gospels

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).

Natalis Invicti

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.

Conclusion

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.

Further reading:

• Was Jesus Really Born on Dec 25? Yes – A Biblical Argument for the Birth of Christ in Late December
• Objections to Christmas and the Dec. 25th Birth of Christ Answered

More than likely the answer to the OP is yes; the choice of 12/25 as Christ's birth came out from the Roman festival of Brumalia. Brumalia evidently means shortest or briefest, which corresponds to the winter solstice day.

This choice of days is not without some forced misunderstanding of metaphor from scripture wherein John the Baptist said he must decrease and Christ must increase.

He must increase, but I must decrease. He that cometh from above is above all: he that is of the earth is earthly, and speaketh of the earth: he that cometh from heaven is above all. John 3:30-31

The context of John's statement, however, was not about natural phenomenom, but about mission and purpose as shown in verse 31.

For the church originally, not much thought was given to the observance of birth days. Origen believed only pagans observed birthdays.

Christmas was not among the earliest festivals of the Church. Irenaeus and Tertullian omit it from their lists of feasts; Origen, glancing perhaps at the discreditable imperial Natalitia, asserts (in Lev. Hom. viii in Migne, P.G., XII, 495) that in the Scriptures sinners alone, not saints, celebrate their birthday; -NewAdvent-

Subsequently, the church recognized January 6th as the day of birth. Their thinking was based on Adam's creation on day 6. They thought their 1/1 aligned to God's timetable of creation.

In Cyprus, at the end of the fourth century, Epiphanius asserts against the Alogi (Hær., li, 16, 24 in P.G., XLI, 919, 931) that Christ was born on 6 January and baptized on 8 November. Ephraem Syrus (whose hymns belong to Epiphany, not to Christmas) proves that Mesopotamia still put the birth feast thirteen days after the winter solstice; i.e. 6 January; -ibid-

At Rome the cult of the sun was far too important to consider a date some 13 days too late.

At Rome the earliest evidence is in the Philocalian Calendar (P.L., XIII, 675; it can be seen as a whole in J. Strzygowski, Kalenderbilder des Chron. von Jahre 354, Berlin, 1888), compiled in 354, which contains three important entries. In the civil calendar 25 December is marked "Natalis Invicti". -ibid-

Natalis Invicti is another name for Sol Invictus or the unconquered sun). This of course refers to the sun "dying" as the days shorten until the winter solstice on 12/25 and then "reviving" as the days lengthen again. This was part of Roman culture.

Sol Invictus ("Unconquered Sun") was the official sun god of the later Roman Empire and a patron of soldiers. On 25 December AD 274, the Roman emperor Aurelian made it an official cult alongside the traditional Roman cults. -source-

Indeed the Catholic Encyclopedia will agree with this association.

The well-known solar feast, however, of Natalis Invicti, celebrated on 25 December, has a strong claim on the responsibility for our December date. -source-

Chrysostom will address this link and try to Christianize it.

"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." -ibid-

So, to answer the OP, yes the choice of 12/25 as the birthday of the Son would be very likely associated with the so-called birth of the sun in pagan religions.

PS I would agree that Christ was most likely born at Tabernacles in the Fall and circumcised on the 8th day of that feast.

The Bible gives no information on the birth date of Jesus. So we do not know if Jesus' birth date was December 25 and any date is speculation. However, the Bible is clear that Jesus was born and so it is appropriate to accept that as fact. While some condemn the practice of celebrating His birth at the time of Christmas, failing to recognize the event as real and something to celebrate seems to be contrary to how His birth was acknowledged by those who knew the date:

⁸ And in the same region there were shepherds out in the field, keeping watch over their flock by night. ⁹ And an angel of the Lord appeared to them, and the glory of the Lord shone around them, and they were filled with great fear. ¹⁰ And the angel said to them, “Fear not, for behold, I bring you good news of great joy that will be for all the people. ¹¹ For unto you is born this day in the city of David a Savior, who is Christ the Lord. ¹² And this will be a sign for you: you will find a baby wrapped in swaddling cloths and lying in a manger.” ¹³ And suddenly there was with the angel a multitude of the heavenly host praising God and saying,

¹⁴ “Glory to God in the highest, and on earth peace among those with whom he is pleased!”

¹⁵ When the angels went away from them into heaven, the shepherds said to one another, “Let us go over to Bethlehem and see this thing that has happened, which the Lord has made known to us.” ¹⁶ And they went with haste and found Mary and Joseph, and the baby lying in a manger. ¹⁷ And when they saw it, they made known the saying that had been told them concerning this child. ¹⁸ And all who heard it wondered at what the shepherds told them. ¹⁹ But Mary treasured up all these things, pondering them in her heart. ²⁰ And the shepherds returned, glorifying and praising God for all they had heard and seen, as it had been told them. (Luke 2) [ESV]

If an angel, the heavenly host, and shepherds saw fit to proclaim and celebrate the birth, surely all who believe in this birth may likewise acknowledge and celebrate.

If I were to venture a guess, here are 2 Biblical possibilities:

1. Passover
2. First day of Booths

First, these are two of the three times a year all men are to be in Jerusalem and it seems likely God would orchestrate this momentous occasion accordingly.

Second, since the Passover is the time of His death a Passover birth would mean He died on the same day as He was born. This would follow the extra-Biblical traditions for Reuben and Moses:

• Reuben born and died on 14 Kislev
• Moses born and died on 7 Adar

Jacob's first born died on his birth date; God's monogenesis Son died on His birth date. Moses, the giver of Law died on his birth date; Jesus the Giver of Life died on His birth date.

Third, Booths became the time of year for ordination of kings; it was also the time of year at which Solomon dedicated the Temple (1 Kings 8; 2 Chronicles 5:3). If Jesus was born on the first day Booths, His circumcision would have taken place on the eighth day, a special Sabbath observed after the 7-days of Booths.