Because the Roman pagan festival of Saturnalia (Saturn) was celebrated from 21 to 25 December, Pope Julius I decreed that Christmas was to be celebrated on 25 December, so that the pagan festival had a Christian setting.
The constitution of the Chancery, which in the case of the Holy See seems to date back to a schola notariorum, with a primicerius at its head, of which we hear under Pope Julius I (337–352), varied from period to period, and the part played by the different officials composing it necessarily varied also.
Julius is also credited with splitting the birth of Jesus into two distinct celebrations: Epiphany stayed on the traditional date, and Nativity was added on 25 December.
Pope Julius I (died 352), pope from February 6, 337 to April 12, 352
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