445 – Obtained from Valentinian III a famous rescript confirming the supremacy of the bishop of Rome.
449 – As archdeacon under Pope Leo I he fought vigorously for the rights of the Roman See and vigorously opposed the condemnation of Flavian of Constantinople at the Second Council of Ephesus to settle the question of Eutyches.
461 – Hilary, Pope Hilarius, The Sardinian archdeacon of Rome, Hilarius was elected bishop of Rome probably on the 17th of November 17.
462 – Convoked a synod, in which confirmed Hermes as titular bishop, withholding his faculties as metropolitan (Wace). Other decisions expressed in an encyclical were in the interests of increased discipline: A synod was to be convened yearly by the Bishop of Arles, but all important matters were to be submitted to the Apostolic See.
463 – Mamertus of Vienne had consecrated a Bishop of Die, although this Church, by a decree of Leo I, belonged to the metropolitan Diocese of Arles. When Hilarus heard of it he deputed Leontius of Arles to summon a great synod of the bishops of several provinces to investigate the matter.
464 – The synod took place and, on the strength of the report given him by Bishop Antonius, he issued an edict on the 25th of February, in which Bishop Veranus was commissioned to warn Mamertus that, if in the future he did not refrain from irregular ordinations, his faculties would be withdrawn.
465 – The Roman synod on the 19th of November, held in the basilica of Santa Maria Maggiore, which settled the matters, is the oldest Roman synod whose original records have survived.
467 – Worked zealously to counter the new emperor’s edict of toleration for schismatic sects, inspired, according to a letter of Pope Gelasius I by a favourite of Emperor Anthemius named Philotheus, who espoused the Macedonian heresy.
468 – Died on the 28th of February 28 in Rome, Italy.