Christians assimilated this feast as the birthday of Jesus, associating him with the “Sun of righteousness” mentioned in Malachi 4:2 (Sol Iustitiae).
The purpose for the choice of 25 December for the celebration of the birth of Jesus was to Christianize the pagan festival in Rome of the Dies Natalis Solis Invicti, meaning “the birthday of the Unconquered Sun”, a festival inaugurated by the Roman emperor Aurelian (270–275) to celebrate the sun god and celebrated at the winter solstice, 25 December. Early Christians assimilated this feast as the birthday of Jesus, associating him with the “Sun of righteousness” mentioned in Malachi 4:2 (Sol Iustitiae).
Prior to and through the early Christian centuries, winter festivals—especially those centered on the winter solstice—were the most popular of the year in many European pagan cultures. Reasons included the fact that less agricultural work needed to be done during the winter, as well as an expectation of better weather as spring approached. Many modern Christmas customs have been directly influenced by such festivals, including gift-giving and merrymaking from the Roman Saturnalia, greenery, lights, and charity from the Roman New Year, and Yule logs and various foods from Germanic feasts.
It was a custom of the Pagans to celebrate on the same 25 December the birthday of the Sun, at which they kindled lights in token of festivity. In these solemnities and revelries the Christians also took part. Accordingly when the doctors of the Church perceived that the Christians had a leaning to this festival, they took counsel and resolved that the true Nativity should be solemnised on that day.”
This view has been seriously challenged by a view based on an old tradition, according to which the date of Christmas was fixed at nine months after 25 March, the date of the vernal equinox, on which the Annunciation was celebrated. This alternative view is considered academically to be “a thoroughly viable hypothesis”, though not certain. The Jewish calendar date of 14 Nisan was believed to be that of creation, as well as of the Exodus and so of Passover, and Christians held that the new creation, both the death of Jesus and the beginning of his human life, occurred on the same date. It was a traditional Jewish belief that great men lived a whole number of years, without fractions, so that Jesus was considered to have been conceived on 25 March, as he died on 25 March, which was calculated to have coincided with 14 Nisan.
Sextus Julius Africanus (c. 160 – c. 240) gave 25 March as the day of creation and of the conception of Jesus.
In his work Adversus Haereses, Irenaeus (c. 130–202) identified the conception of Jesus as March 25 and linked it to the crucifixion at the time of the equinox, with the birth of Jesus nine months after on 25 December at the time of the solstice.
The tractate De solstitia et aequinoctia conceptionis et nativitatis Domini nostri Iesu Christi et Iohannis Baptistae falsely attributed to John Chrysostom also argued that Jesus was conceived and crucified on the same day of the year and calculated this as 25 March. This anonymous tract also states: “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.”
With regard to a December religious feast of the sun as a god (Sol), as distinct from a solstice feast of the (re)birth of the astronomical sun, one scholar has commented that, “while the winter solstice on or around December 25 was well established in the Roman imperial calendar, there is no evidence that a religious celebration of Sol on that day antedated the celebration of Christmas”. “Although the Emperor Aurelian’s dedication of a temple to the sun god in the Campus Martius (C.E. 274) took place on the ‘Birthday of the Invincible Sun’ on December 25, the cult of the sun in pagan Rome ironically did not celebrate the winter solstice nor any of the other quarter-tense days, as one might expect.”
25 December was chosen for celebrating the birth of Jesus on the basis of the belief that his conception occurred on 25 March “potentially establishes 25 December as a Christian festival before Aurelian’s decree, which, when promulgated, might have provided for the Christian feast both opportunity and challenge”.
The Christian ecclesiastical calendar contains many remnants of pre-Christian roman festivals. Christmas includes elements of the Roman feast of the Saturnalia and the birthday of Mithra. The Chronography of 354 AD contains early evidence of the celebration on December 25 of a Christian liturgical feast of the birth of Jesus. This was in Rome, while in Eastern Christianity the birth of Jesus was already celebrated in connection with the Epiphany on January 6. The December 25 celebration was imported into the East later: in Antioch by John Chrysostom towards the end of the 4th century, probably in 388, and in Alexandria only in the following century. Even in the West, the January 6 celebration of the nativity of Jesus seems to have continued until after 380. In 245, Origen of Alexandria, writing about Leviticus 12:1–8, commented that Scripture mentions only sinners as celebrating their birthdays, namely Pharaoh, who then had his chief baker hanged (Genesis 40:20–22), and Herod, who then had John the Baptist beheaded (Mark 6:21–27), and mentions saints as cursing the day of their birth, namely Jeremiah (Jeremiah 20:14–15) and Job (Job 3:1–16). In 303, Arnobius ridiculed the idea of celebrating the birthdays of gods, a passage cited as evidence that Arnobius was unaware of any nativity celebration. Since Christmas does not celebrate Christ’s birth “as God” but “as man”, this is not evidence against Christmas being a feast at this time. The fact the Donatists of North Africa celebrated Christmas may indicate that the feast was established by the time that church was created in 311.
Christmas was promoted in the Christian East as part of the revival of Catholicism following the death of the pro-Arian Emperor Valens at the Battle of Adrianople in 378. The feast was introduced to Constantinople in 379, and to Antioch in about 380. The feast disappeared after Gregory of Nazianzus resigned as bishop in 381, although it was reintroduced by John Chrysostom in about 400.
The prominence of Christmas Day increased gradually after Charlemagne was crowned
Emperor of the Holy Roman Empire on Christmas Day in 800.
[Charlemagne (KAROLVS IMP AVG (Karolus Imperator Augustus) reached the height of his power in 800 A.D. when he was crowned Emperor of the Romans by Pope Leo III on Christmas Day at Old St. Peter’s Basilica. Charlemagne continued his father’s policy towards the papacy and became its protector, removing the Lombards from power in northern Italy, and leading an incursion into Muslim Spain. He also campaigned against the Saxons to his east, Christianizing them upon penalty of death, leading to events such as the Massacre of Verden.
Called the “Father of Europe” (pater Europae), Charlemagne united most of Western Europe for the first time since the Roman Empire. His rule spurred the Carolingian Renaissance, a period of energetic cultural and intellectual activity within the Church. Both the French and German monarchies considered their kingdoms to be descendants of Charlemagne’s empire.]
Many popular customs associated with Christmas developed independently of the commemoration of Jesus’ birth, with certain elements having origins in pre-Christian festivals that were celebrated around the winter solstice by pagan populations who were later converted to Christianity. These elements, including the Yule log from Yule and gift giving from Saturnalia, became syncretized into Christmas over the centuries. The prevailing atmosphere of Christmas has also continually evolved since the holiday’s inception, ranging from a sometimes raucous, drunken, carnival-like state in the Middle Ages, to a tamer family-oriented and children-centered theme introduced in a 19th-century transformation. Additionally, the celebration of Christmas was banned on more than one occasion within certain Protestant groups, such as the Puritans, due to concerns that it was too pagan or unbiblical.
Countries have adopted many of the secular aspects of Christmas, such as gift-giving, decorations, and Christmas trees.
https://en.m.wikipedia.org/wiki/Christmas
https://treskia.wordpress.com/dies- natalis solis invicti
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