Roman calendar, the Chronography of 354 (or calendar of Filocalus), has survived. This calendar lists a festival for Sol and Luna on August 28, Ludi Solis (games for Sol) for October 19-22, and a Natalis Invicti (birthday of the invincible one) on December 25. While it is widely assumed that the invictus of December 25 is Sol, the calendar does not state this explicitly. The only explicit reference to a celebration of Sol in late December is made by Julian the Apostate in his hymn to King Helios written immediately afterwards in early CE 363. Julian explicitly differentiates between the one-day, annual celebration of late December 362 and the multi-day quadrennial games of Sol which, of course, had also been held in 362, but clearly at a different time. Taken together, the evidence of the Calendar of Filocalus and Julian’s hymn to Helios clearly shows, according to Hijmans and others, that the ludi of October 19 – 22 were the Solar Games instituted by Aurelian. They presumably coincided with the dedication of his new temple for Sol.
4. After Aurelian, Sol became supreme deity of the Roman Empire.
(Hijmans 2009, chapter 9) raises serious doubts about this contention.
Constantine
Coin of Emperor Constantine I depicting Sol Invictus with the legend SOLI INVICTO COMITI, circa 315.
Identical reverse as above but with Emperor Licinius on head
Emperors portrayed Sol Invictus on their official coinage, with a wide range of legends, only a few of which incorporated the epithet invictus, such as the legend SOLI INVICTO COMITI, claiming the Unconquered Sun as a companion to the Emperor, used with particular frequency by Constantine. Statuettes of Sol Invictus, carried by the standard-bearers, appear in three places in