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325 Council of Nicea, (First Ecumenical - Imperial Council),  convened by Roman Emperor, St. Constantine the Great. It is attended by 318 fathers, including Sts. Athanasius the Great, Nicholas of Myra, Spyridon of Trimythus, Alexander of Constantinople, Alexander of Alexandria, Eustace of Antioch, Macarius of Jerusalem, and the legates of St. Sylvester of Rome. It condemns the Arians (also known as Lucianists, who believe the Son was created), Paulians (also known as Sabellians, who believe the Father, Son and Holy Spirit is the same person), Quartodecimans (those who celebrate Pascha on Nisan 14) and Meletians (those who caused a schism and parallel hierarchy in Egypt). This council also formulates the Nicene Creed, sets a united date for celebrating Pascha, condemns mandatory celibacy for clergy, establishes regulations on morality and discipline, decides Christians ought to stand, not kneel, while praying on Sunday, and establishes Rome, Alexandria and Antioch as the three equal spiritual centers (Patriarchates) of Christianity.

326 Discovery of the True Cross by the Empress Helena; King Miraeus of Georgia becomes Christian.

328 Athanasius the Great becomes bishop of Alexandria.

329 Athanasius ordains Frumentius (Abba Selama) to priesthood and commissions him to evangelize Ethiopia.

330 Byzantium refounded as Constantinople / New Rome, Christian capital of the Roman Empire, and is dedicated to the Theotokos by Emperor Constantine; Amoun and Macarius the Great found monasteries in the Egyptian desert.

336-338 Athanasius the Great goes into exile in Treves, telling Europeans about the monastic rule of Pachomius the Great, awakening interest in monasticism in Europe.

337 Death of Constantine.

340 Conversion of Wulfila to Arianism.

341 Council of Antioch held; Emperor Constans bans pagan sacrifices and magic rituals under penalty of death.

345 Death of Nicholas of Myra.

348 Death of Pachomius the Great and Spyridon of Trimythous.

350 Ninian establishes the church Candida Casa at Whithorn in Galloway, Scotland, beginning the missionary effort to the Picts.

351 Apparition of the Cross over Jerusalem.

355 Death of Nino of Cappadocia.

356 Death of Anthony the Great.

357 Council of Sirmium issues Blasphemy of Sirmium.

358 Basil the Great founds monastery of Annesos in Pontus, the model for Eastern monasticism.

359 Councils of Seleucia and Rimini.

360 Martin of Tours founds first French monastery at Liguge; first church of Hagia Sophia inaugurated by Emperor Constantius II.

362 Antiochian schism (362-414).

361-63 Julian the Apostate becomes Roman emperor and attempts to restore paganism.

363 Emperor Jovian reestablishes Christianity as the official religion of the Empire.

364 Council of Laodicea held.

367 Athanasius of Alexandria writes Paschal letter, listing for the first time the canon of the New Testament; death of Hilary of Poitiers.

373 Death of Athanasius the Great and Ephrem the Syrian.

374 Election of Ambrose as bishop of Milan.

375 Basil the Great writes On the Holy Spirit.

376 Visigoths convert to Arian Christianity.

379 Death of Basil the Great; Emperor Gratian's rescript Ordinariorum Sententias extends power of Bishop of Rome by allowing him authority over bishops within his own jurisdiction.

380 Christianity established as the official faith of the Roman Empire by Emperor Theodosius the Great; Council of Saragossa condemns Priscillianism.

381 Council of Constantinople (Second Ecumenical), convened by Roman Emperor Theodosius the Great, presided over at first by St. Meletius of Antioch, and, following his repose, by St. Gregory the Theologian, Patriarch of New Rome, and attended by 150 bishops of both east and west. It condemns the Arians (also known as Eunomians or Eudoxians, who believe Christ is created, and of a completely different essence to the Father), Semi-Arians (who believe Christ is of a similar, yet different, essence to the Father), Macedonians (or Pneumatomachi, who believe the Holy Spirit is a mere creature), Apollinarians (who believe Christ has a human body and soul, but not a human rational mind), Sabellians (who believe the Father, Son and Holy Spirit are one and the same person), Marcellians (who believe the Son and Holy Spirit are not eternal persons, but are transitions of the Father that would again unite into one person with the Father at the end of time), Photinians (who believe Christ is a mere man), Millenarians (who believe in the literal thousand-year reign), and Quartodecimans (who celebrate Pascha on Nisan 14). This council reaffirms that Christians must stand while praying on Sundays and the days from Pascha to Pentecost. It recognizes Old Rome, Constantinople (New Rome), Alexandria, Antioch and Jerusalem as the five spiritual centers (Patriarchates) of the Christian Empire. This council also attempts to resolve the Antiochian schism since St. Meletius had reposed. St. Flavian is elected and enthroned as his successor. However, he is later rejected by the bishops of the West, Egypt, Arabia, Africa and Cyprus, who recognize Paulinus, and later his successor, Evagrius, as Bishop of Antioch.

382 Pope Siricius of Rome first to bear title Pontifex Maximus.

383 Death of Frumentius of Axum, bishop of Axum and Apostle to Ethiopia.

384 Council of Bordeaux condemns Priscillian.

385 Death of Gregory of Nyssa.

386 Death of Cyril of Jerusalem.

387 Augustine baptized by Ambrose of Milan.

391 Death of Gregory the Theologian.

391-92 Closing of all non-Christian temples in the Empire; Theodosius the Great ends pagan Eleusinian Mysteries by decree and causes surviving pagan sacrifices at Alexandria and Rome to cease.

392 Death of Macarius the Great.

393 Council of Hippo publishes Biblical canon; Emperor Theodosius bans Olympic Games as a pagan festival.

394 Epiphanius of Salamis attacks teachings of Origen as heretical; Council of Constantinople held; Donatist Council of Bagai in Africa held.

395 Augustine becomes bishop of Hippo in North Africa; placing of the cincture of the Theotokos in the Church of the Virgin in Halkoprateia-Constantinople.

395 Re-division of Empire with death of Emperor Theodosius the Great.

397 Council of Carthage publishes Biblical canon; death of Martin of Tours and Ambrose of Milan.

398 John Chrysostom becomes Archbishop of Constantinople.

398 Martyrdom of 10,000 Fathers of the Scetis by Patriarch Theophilus of Alexandria.

399 Anastasius I of Rome and other bishops condemn doctrine of Origen.

401 Augustine of Hippo writes Confessions; Pope Innocent I of Rome supports John Chrysostom and condemns pelagianism.

402 Porphyry of Gaza obtains imperial decree ordering closing of pagan temples in Gaza.

403 Abduction of Patrick to Irelande; visit of Victricius of Rouen to Britain; Synod of the Oak held near Chalcedon, deposing and exiling John Chrysostom.

404 Martyrdom of Telemachus, resulting in Emperor Honorius' edict banning gladiator fights.

405 Translation of Holy Scriptures into Latin as the Vulgate by Jerome.

407 Death of John Chrysostom in exile.

410 Fall of Rome to the Visigoths under Alaric I; escape of Patrick back to Britain; Emperor Honorius tells Britain to attend to its own affairs, effectively removing the Roman presence.

410 Council of Seleucia declares Mesopotamian Nestorian bishops independent of Orthodox bishops.

411 Pelagius condemned at council in Carthage; Rabbula becomes bishop of Edessa.

412 Cyril succeeds his uncle Theophilus as Pope of Alexandria; Honorius outlaws Donatism; Bishops Lazarus of Aix-en-Provence and Herod of Arles expelled from sees on a charge of Manichaeism; Alexandrian Creation Era date finalized at 25 March, 5493 BC.

414 Resolution of Antiochian division.

415 Pelagius cleared at synod in Jerusalem and a provincial synod in Diospolis (Lydda); John Cassian founds convent at Marseilles.

416 Councils in Carthage and Milevis condemn Pelagius and convince Pope Innocent I of Rome to excommunicate him.

418 Foundation of the Arian Visigothic Kingdom, as Emperor Honorius rewards Visigoth federates by giving them land in Gallia Aquitania on which to settle.

418-24 Council in Carthage anathematizes Pelagianism by way of endorsing Augustinian anthropology.

426 Augustine of Hippo writes The City of God.

428 Nestorius becomes patriarch of Constantinople.

429 Pope Celestine I dispatches prominent Gallo-Roman Bishops Germanus of Auxerre and Lupus of Troyes to Britain as missionary bishops and to combat the Pelagian heresy; death of Sisoes the Great.

430 Peter the Iberian founds Georgian monastery near Bethlehem.

431 Council of Ephesus (Third Ecumenical), convened by Emperor Theodosius II, presided over by Pope St. Cyril of Alexandria, and attended by more than 200 fathers. It condemns Nestorianism (the belief that the person of Christ consists of two hypostases, a human and a divine, and that the Theotokos is therefore to be called Christotokos, as if Christ is not God). It also confirms the Nicene-Constantinopolitan Creed, and declares any additions or subtractions to it are henceforth forbidden. It is also declared that bishops are not to interfere in the vicinities and dioceses of other bishops.

432 Return of Patrick to Ireland to begin missionary work; death of Ninian, Apostle to the Picts.

433 Formulary of Peace completes work of Third Ecumenical Council by reconciling Cyril of Alexandria with John of Antioch.

435 Death of John Cassian and Acacius of Melitene; Nestorius exiled by imperial edict to a monastery in a Sahara oasis.

438 Codex Theodosianus published.

439 Carthage falls to Vandals.

444 Death of Cyril of Alexandria; Pope Leo the Great abolishes Gallican vicariate.

445 Founding of monastery at Armagh in northern Ireland; Emperor Valentinian III issues decree recognizing primacy of the bishop of Rome.

447 Earthquake in Constantinople, when a boy was lifted up to heaven and heard the Trisagion.

449 Robber Synod of Ephesus, presided over by Dioscorus of Alexandria, with an order from the emperor to acquit Eutyches the Monophysite.

450 First monasteries established in Wales; death of Peter Chrysologus.

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