Pope Marcus died on October 7, 336. No one was elected to replace him until February 6, the next year. At that time, Julius, son of Rustics, a Roman, was raised to the Chair of Peter.
Almost as soon as Julius was proclaimed, the great emperor, Constantine died. He, it is recalled, tended to favor the new heresy, the Arians, who insisted that Jesus was the Son, but created in time, and therefore not equal to the Father. Some said he was only human. And Constantine had allowed Athanasius, bishop of Alexandria, to be deposed and exiled. The emperor's son, Constantine II, the governor of Gaul, favored the orthodox and let Athanasius back from exile to take up his bishopric again.
The problem was that the Arians of Egypt had set up Pistus as their bishop and had sent ambassadors to Julius to admit Pistus into communion with Rome, quoting the decisions of their Council of Tyre (335) to prove that their deposition of Athanasius was valid. Meanwhile, Athanasius sent a deputation to Julius with a letter from the Egyptian bishops quoting their synod's justification of Athanasius. The two groups met with Julius and he proposed a third synod to present the case. Julius invited the Eastern bishops to come. Unfortunately, the Arian bishops held their own synod at Antioch and elected George of Cappadocia to replace Pistus and Athanasius was exiled again. Needless to say, few of the Eastern bishops came to the synod. They simply took over a number of sees and put heretical men in.
The synod in Rome found Athanasius to be wholly orthodox and reinstated him. Juliu wrote to the Arian bishops and explained in detail his conclusions. He also berated them for not showing. He pointed ou6t the traditional form for resolving problems, "Can you be ignorant that this is the custom, that we should be written to first, so that from here, what is just may be defined." This is the first extant argument for papal supremacy.
The arguments did not end there. And another council of all bishops was proclaimed by the emperors (Constantine's sons) and Julius to be held in Sardica (now Sofia, Bulgari). Julius sent ambassadors and 300 Western bishops attended. The Aria bishops refused to attend and wrote their own creed and deposed Julius. The Western half defined the procedure against accused bishops and the papal intervention in condemnation of bishops.
Athanasius spent several years in Rome before finally returning to his see. While there, he taught the faithful about Egyptian monastic life, an unknown entity so far. Many Westerners thought the next centuries adapted this lifestyle.
Julius was busy with many other subjects besides the Arians, however. He ordered built two basilicas, including S. Maria in Trasteverde, and built three churches over cemeteries. The number of faithful in the Roman environs kept growing quickly. To educate those of the Faith, Julius ensured that catalogues of saint feast days come into use. He also ordered all official acts to be recorded and preserved, making him essentially the founder of the Vatican archives.
This pope is also credited with defining the date of Christmas. At that time, it was considered that a great man would only live whole years, not fractions of years. Thus, he would die on the date of his conception. Going back through the years,
researchers determined that Jesus would have died on March 25, since that was the day of the Passover in the year of His death. Since he was perfect, it was assumed that he would have also been conceived on that date and, of course, be born exactly nine months later, making His birth date December 25.
After such a busy career, Pope Julius I died on April 12, 352 and was buried in the catacombs of Caleopdius. His remains were eventually moved to S. Maria in Trasteverde.