Born in Rome, Pope St. Julius I was elected pope on February 6, 337 and reigned for 15 years. He knew the great St. Athanasius, who was the on-again-off-again Bishop of Alexandria at the time, and even spoke up on his behalf when Athanasius’ enemies sought to remove him (more on that in a minute). Julius I died on April 12 (352), the same day on which his feast is now celebrated, and he was buried in a church he constructed attached to the cemetery of St. Callixtus.

With the Arian heresy still brewing within the Church, St. Julius I is best known for firmly making his presence known in one particular dispute that took place in the eastern part of the Church. As mentioned, when Athanasius was Bishop of Alexandria he was deposed once, then restored through the intervention of the emperor, Constantine II. Then, at the same time that a certain Eusebius (not the pope or the historian) sent delegates to the pope trying to get him removed again, Athanasius was deposed again, but by a different group back in Alexandria. So, Pope Julius, wanting to resolve it once and for all, wrote to both parties and invited them to Rome, saying, “you bring your gripes, I’ll bring the chips and salsa.” 

This meeting - called a synod - was convened in 340 or 341, with the honorable Pope Julius I presiding. After hearing both sides of the story, Julius declared in favor of Athanasius and Marcellus (another legit bishop who had been deposed) and restored them both to office. In his letter (which still exists) written to the heretical bishops of Antioch, who had conveniently skipped out on this meeting in Rome, Julius wrote, “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?” Julius said this because he knew it was uniquely his place as the pope to depose bishops -- something that was confirmed in a general council just a year or two later.

Fun fact: We can thank St. Julius I for officially determining that Christmas, the Nativity of Jesus, would be celebrated on December 25, while Epiphany would stay on January 6. Earlier records show that the Church had already been commemorating this day for at least 100 years earlier, but Julius wanted to make it official. Read more here on why December 25 might actually be the birthdate of Jesus.