The claim is that Sol Invictus “Invincible Sun” is a more ancient pagan holiday in Rome celebrated on December 25th. The claim assumes that this pagan holiday was so popular and dangerous that the Christian Church sought to suppress it by establishing the celebration of Christ’s Nativity on December 25th. By doing this, the claim continues, the Christians adopted the pagan day and some of the practices of that pagan festival to make the celebration of Christmas more appealing to pagans. . . .
While pagan worship of the sun certainly existed in Rome before the spread of the fulfillment of that promise in Christ came to the city; the celebration of Sol Invictus as a god in Rome actually came as pagans attempted to suppress Christianity. This early attempt as suppressing Christianity by means of the pagan worship of Sol is found in the Historia Augusta, a pagan history of Rome compiled in the fourth century AD.
The Historia Augusta in The Life of Elagabalus (1.3) relates events from the Roman Emperor Marcus Aurelius Antoninus Augustus, a particularly twisted man, who reigned from 218-222 AD. Marcus Aurelius Antoninus came to be called Elagabalus after the name of the Syrian sun god, and was himself initiated as a priest of that false god. He viewed himself as the personal manifestation of the Syrian sun god. After coming to Rome and being established as emperor at the age of 14, the Historia states:
4 Elagabalus [established himself] as a god on the Palatine Hill close to the imperial palace; and he built him a temple, to which he desired to transfer the emblem of the Great Mother, the fire of Vesta, the Palladium, the shields of the Salii, and all that the Romans held sacred, purposing that no god might be worshipped at Rome save only Elagabalus. 5 He declared, furthermore, that the religions of the Jews and the Samaritans and the rites of the Christians must also be transferred to this place, in order that the priesthood of Elagabalus might include the mysteries of every form of worship. [Latin]
And, coincidentally, very shortly after Elagabalus tried to establish worship of the Syrian sun god, Sol Invictus, he was thought to be too licentious and was assassinated by his own people, pagan Romans, at the age of 18 years old.
From that time there is no mention of the celebration of Sol Invictus in Roman history until the rule of Aurelian (A.D. 270-275). Aurelian did try to re-introduce the worship of Sol Invictus by decree in the year 274. But there is no record of this festival being held on December 25th. “The traditional feast days of Sol, as recorded in the early imperial fasti, were August 8th and/or August 9th, possibly August 28th, and December 11th.”(Hijmans, p. 588 )
Aurelian did declare games to Sol every four years. But there is no record from the period or early historiographers that these games were associated with December 25th in any way. The best evidence suggest that the games were held October 19-22 of their calendar. Anyway, on another coincidence, a year after Aurelian declared these games in honor of Sol Invictus, he was assassinated by his own pagan Roman officers out of fear he would execute them based on false charges.
The earliest calendar to mention that Invictus as a specified date for Roman religious life comes from a text of the Philocalian Calendar, VIII Kal recorded in an illuminated 4th Century manuscript called The Chronography of 354. In this late manuscript the date is listed in Mensis December (The Month of December) as N·INVICTI·CM·XXX.
Many scholars through the years have assumed that INVICTI in this calendar must mean “Sol Invictus.” This is possible. However, elsewhere the calendar does not hesitate to make explicit mention of festivals to Sol, for example: on SOLIS·ET·LVNAE·CM·XXIIII (August 28th) and LVDI·SOLIS (October 19-22).
Even if INVICTI does refer to Sol Invictus on December 25th of this calendar, all this shows is that the celebration of Sol Invictus was placed on December 25th after Christianity had already widely accepted and celebrated December 25th as the Nativity of Christ.
There are many historians and people following them who will still assert that December 25th is Sol Invictus in ancient Rome. Some will even claim that another religion, Mithraism, has close connection to this December 25th celebration. In actual fact there is no ancient documentation tying Mithraism to December 25th or Sol Invictus. The Christian celebration of the Nativity of Christ as December 25th predates anything in the earliest actual documentation for Sol Invictus on December 25th.
via Steadfast Lutherans » Redeeming Holy Days from Pagan Lies — Christmas and Sol Invictus.