Pope Julius I was the bishop of Rome from 6 February 337 to his death on 12 April 352. He was appealed to by Athanasius when the latter was deposed from his position as patriarch by Arian bishops, Julius then supported Athanasius and condemned his deposition as unjust. He was notable for asserting the authority of the pope over the Arian Eastern bishops, as well as being attributed with the setting of December 25 as the official birthdate of Jesus.
Pontificate
Julius was a native of Rome and was chosen as successor of Pope Mark after the Roman seat had been vacant for four months.
Arianism
Julius is chiefly known by the part he took in the Arian controversy. After the followers of Eusebius of Nicomedia, who had become the patriarch of Constantinople, renewed their deposition of Athanasius of Alexandria at a synod held in Antioch in 341, they resolved to send delegates to Constans, emperor of the West, and also to Julius, setting forth the grounds on which they had proceeded. Julius, after expressing an opinion favourable to Athanasius, adroitly invited both parties to lay the case before a synod to be presided over by himself. This proposal, however, the Arian Eastern bishops declined to accept.
On this second banishment from Alexandria, Athanasius came to Rome, and was recognised as a regular bishop by the synod presided over by Julius in 342. Julius sent a letter to the Eastern bishops that is an early instance of the claims of primacy for the bishop of Rome. Even if Athanasius and his companions were somewhat to blame, the letter runs, the Alexandrian Church should first have written to the pope. "Can you be ignorant," writes Julius, "that this is the custom, that we should be written to first, so that from here what is just may be defined" (Epistle of Julius to Antioch, c. xxii).
By its 3rd, 4th, and 5th decrees relating to the rights of revision claimed by Julius, the council of Sardica perceptibly helped forward the claims of the bishop of Rome. Julius built several basilicas and churches.
Christmas
Some have stated that, around 350 AD, Julius I declared December 25 as the official date of the birth of Jesus; this is based on a letter quoted only in a 9th-century source, and this letter is spurious. At the time this was one of the commonly believed dates for Jesus' birth and was used by Hippolytus of Rome in his Commentary on Daniel around 200 AD. It is claimed – falsely – that Pope Julius declared December 25 as Christmas after patriarch Cyril of Jerusalem asked for clarification on what date historical records stored in Rome indicate as Jesus' birth. It was also believed that Jesus and John the Baptist were born around the same time from reading the Gospel of Luke.
The actual date of Jesus's birth is unknown. It has been noted that 25 December is two days after the end of the Roman festival of Saturnalia. Some have speculated that part of the reason this date was chosen may have been because Julius was trying to create a Christian alternative to Saturnalia. He may have also been influenced by the idea that Jesus had died on the anniversary of his conception;