Timeline of Rome

4th Century AD – Christianity and Rome Splits in two

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The 4th century AD brought sweeping transformations across the Roman Empire—politically, socially, and religiously. Emperors from Diocletian to Theodosius enacted far-reaching reforms, from edicts fixing prices and binding workers to their trades to decisive support (or opposition) of emerging Christian authority. Persecution of Christians climaxed under Diocletian but soon gave way to imperial endorsement by Constantine, culminating in Christianity becoming the official state religion under Theodosius. Meanwhile, shifting borders, barbarian incursions, and natural disasters such as earthquakes and eruptions buffeted Italy’s landscape. By century’s end, the Empire was permanently split between East and West, its pagan temples shuttered, and the age-old Olympic Games were abolished—marking the dawn of a new era.

Dioceses Established in the 4th Century

  • Acerenza, Bari, Brindisi, Lipara, Lucera, Teano.

301 AD

  • 270th Olympiad.
  • Emperor Diocletian issues new edicts:
    • Tradesmen must remain in their trade; their children must follow them.
    • Tenants must remain on their lands for life—often cited as the legal start of feudalism in Italy.
    • Price Edict fixes wages and prices.
  • Pestilence spreads through Rome and Italy.

302 AD

  • (c.) St. Ampelius and St. Caius executed at Messina.
  • Christians increasingly disrupt pagan ceremonies; Diocletian witnesses such an incident at Nicomedia and is further convinced Christians threaten imperial unity.

303 AD: The Great Persecution

  • (Feb 23/24) Diocletian decrees a general persecution of Christians, aiming to restore traditional Roman religion.
    • Targets chiefly Christian leaders and steadfast believers who refuse to recant.
    • Any Christian who pays homage to Roman gods is freed. Some, like St. Dominica (Campania), deliberately seek martyrdom by destroying pagan idols.
    • St. Lucy is martyred at Syracuse; later the Basilica of Santa Lucia extra Moenia is built on the presumed site.
  • (c.) Eruption of Vesuvius.

304 AD

  • Martyrdom of Santa Lucia, patron saint of Palermo.

305 AD

  • 271st Olympiad.
  • (May 1) Diocletian, age 60, abdicates and retires to Salona in Dalmatia. He compels Maximian to abdicate, too.
  • Galerius and Constantius I Chlorus become the new Augusti; Severus and Maximin Daia become Caesars.

306 AD

  • (July 23) Constantine I is proclaimed Caesar in the West.
  • (July 25) Constantius I Chlorus dies near Eboracum (York). His troops hail Constantine as Augustus.
    • Galerius instead promotes Severus to Augustus.
  • (Oct 28) Maxentius, son of Maximian, is proclaimed Caesar in Rome by the Praetorians.
  • Galerius and Maximin Daia renew persecutions against Christians in the East.
  • Mt. Vesuvius erupts.

307 AD

  • (Nov 11) Emperor Severus dies; Galerius appoints Licinius in his place.
  • Constantine, claiming a better right to the western throne, revolts—gaining Britain and Gaul.
  • Maximian emerges from retirement as Augustus.
  • Another tradition holds St. Lucy is martyred at Syracuse this year (alternate date to 303).

308 AD

  • St. Marcellus I becomes Pope (alt. 306).
    • He tries unsuccessfully to expunge Pope Marcellinus (who lapsed during persecution) from Christian records.
    • Maxentius exiles him for causing civil unrest in Rome.
  • (Summer) L. Domitius Alexander, governor of Africa, rebels against Maxentius, cutting off grain to Rome. A famine ensues until 312.

309 AD

  • 272nd Olympiad.
  • Maxentius banishes his father Maximian to Gaul.
  • Another plague (possibly anthrax) begins, lasting ~5 years.
  • Pope Marcellus I is deposed and exiled, replaced by St. Eusebius I (alt. 310).

310 AD

  • St. Nympha (Ninfa) of Palermo is martyred.
  • Pope Eusebius I and antipope Heraclius are deported to Sicily by Maxentius.
  • Maximian conspires against Constantine in Gaul; the plot is exposed, and Maximian commits suicide.
  • Constantine begins his campaign against Maxentius.

311 AD

  • (Apr 30) Emperor Galerius ends the Great Persecution with the Edict of Serdica (Toleration), except in territories of Maximin Daia who continues persecuting Christians.
  • (May) Maxentius repels Galerius from Italy.
  • (May 5) Galerius dies; his domain is split between Maximin Daia and Licinius, who form a secret alliance with Maxentius.
  • (July 2) St. Miltiades becomes Pope.

312 AD

  • (Oct) On his march to Rome, Constantine sees a celestial sign, interpreted as divine Christian favor. He has soldiers inscribe the Chi-Rho on shields.
  • (Oct 28) Battle of the Milvian Bridge: Constantine decisively defeats Maxentius, who drowns in the Tiber.

313 AD: Edict of Milan

  • 273rd Olympiad.
  • (Mar 1) Constantine and Licinius meet in Milan; issue a joint edict granting freedom of religion and legalizing Christianity.
    • Christians begin aggressively eradicating pagan cults and reclaiming confiscated property.
    • Christians possibly number 1/20 to 1/5 of the empire’s population.
  • Synod in Rome under Pope St. Miltiades, with 19 bishops (including Beneventum, Capua).
  • Constantine grants Pope Miltiades Fausta’s palace in Rome as a papal residence.
  • Emperor Maximinus II Daia dies at Tarsus.
  • Proterio becomes bishop of Capua.

314 AD

  • (Jan 11) Pope St. Miltiades dies; Sylvester I becomes pope (Jan 31).
  • (Oct 8) Battle of Cibalae: Constantine defeats Licinius, who loses all Balkans except Thrace.
  • Council of Arles condemns Donatism.
  • Death of Maximian Daia (alt. name for Maximin Daia).

315 AD

  • Constantine visits Rome but refuses to perform duties as Pontifex Maximus.

316 AD

  • Diocletian dies in retirement.

317 AD

  • 274th Olympiad.

318 AD

  • Constantine bans use of “magic” for murder.
  • Special privileges granted to high Christian clergy (Cod. Theod. I.xxvii.1).

319 AD

  • (Feb 1) Constantine suppresses soothsayers (Theod. Cod. 9.16.1).
  • (Oct 21) Clergy are exempted from public service (Theod. Cod. 16.2).

321 AD

  • 275th Olympiad.
  • Constantine declares Sunday as a public holiday.
  • Lower Christian clergy also gain special privileges.
  • Birth of Valentinian I, future emperor.

322 AD

  • Constantine I launches new campaign vs. Licinius on the lower Danube.

323 AD

  • (July 3) Constantine’s son Crispus defeats Licinius’s fleet near Adrianople.
  • (Sept 18) Constantine routs Licinius at Chrysopolis. Licinius abdicates, leaving Constantine sole Augustus.
  • More privileges granted to lower Christian clergy.

324 AD

  • Constantine chooses Byzantium (on the Bosporus) as his new capital, later Constantinople.
  • (Feb) Licinius is executed by Constantine’s order.
  • Constantine annuls Licinius’s acts.
  • Decree for the Council of Nicaea.
  • Work begins on the first St. Peter’s basilica in Rome.

325 AD: Council of Nicaea

  • 276th Olympiad.
  • (May–Aug) Constantine convenes the council:
    • Condemns Arianism, affirms the Father–Son equality, and adopts the Nicene Creed.
    • Establishes rules for determining Easter’s date.
  • ~318 bishops attend, mostly from the East.

326 AD

  • Constantine visits Rome, confiscates pagan temples, giving them to Christians; also seizes the Palladium of pagan Rome and later buries it in Constantinople.
  • (c.) Calepodius becomes bishop of Naples (to ~347).

328 AD

  • (Nov 4) Constantinople’s site is officially laid out and consecrated.

329 AD

  • 277th Olympiad.
  • Future emperor Valens is born.

330 AD

  • (May 11) Constantine dedicates Constantinople (formerly Byzantium).
  • The first Basilica of St. Peter is completed on the Vatican Hill in Rome.
  • Empire reorganized into prefectures, dioceses, and provinces.

332 AD

  • Future emperor Julian (the Apostate) is born.

333 AD

  • 278th Olympiad.

335 AD

  • Constantine closes certain pagan temples, e.g., those of Asklepios offering public medical care.

336 AD

  • St. Mark (Marcus) becomes pope.
  • First basilica of St. Peter’s is completed in Rome.

337 AD

  • 279th Olympiad.
  • (May 22) Emperor Constantine I dies after baptism by the Arian bishop Eusebius of Nicomedia.
  • Empire splits among his sons:
    • Constantine II (Gaul, Britannia, Hispania),
    • Constantius II (Eastern provinces, Arian supporter),
    • Constans I (Italia, Africa, Illyricum; supports Nicene orthodoxy).
  • A legend claims patrician families bound for Constantinople are shipwrecked on the Campanian coast and settle there, founding Amalfi.
  • Pope Julius I succeeds St. Miltiades.
  • Vincenzo becomes bishop of Capua.

340 AD

  • Constantine II is killed near Aquileia in battle vs. his brother Constans I.
  • Constans gains his provinces.
  • Constans I outlaws paganism (Cod. Theod. XVI.10.2).

341 AD

  • 280th Olympiad.
  • Constantius II forbids pagan sacrifices and orders temple closures (Cod. Theod. XVI.10.2). Pagan temples face looting, destruction, or conversion to churches.

345 AD

  • 281st Olympiad.

346 AD

  • St. Amasius becomes bishop of Teano (Campania), fleeing Arian persecution in Greece.
  • Vesuvius erupts; earthquake affects Abellinum (Avellino), causing abandonment of a grand villa from ~129 BC. Alife (CE) also suffers.
  • Constantius II renews anti-pagan edicts with capital punishment for sacrifices (Cod. Theod. XVI.10.3–4).
  • Birth of Theodosius I in Spain.

347 AD

  • Earliest record of a bishop of Bari—Gervasius attends the Council of Sardica.
  • (c.) Fortunatus I is bishop of Naples (to ~359).

348 AD

  • Rome celebrates its 1100th anniversary (founded 753 BC by tradition).

349 AD

  • 282nd Olympiad.
  • Revolt of Count Magnentius.

350 AD

  • Constans I is killed; Constantius II becomes sole emperor.
  • Constantius II renews anti-pagan measures.
  • First Christmas celebrations in Rome noted.

352 AD

  • St. Aproculus (Proculus), bishop of Brundisium, dies at Ardea returning from Rome.
  • Liberius becomes pope.

353 AD

  • 283rd Olympiad.
  • Constantius II again renews anti-pagan decrees.

355 AD

  • Felix II becomes antipope, backed by Arian Emperor Constantius II.

356 AD

  • Constantius II renews anti-pagan legislation once more.

357 AD

  • 284th Olympiad.

359 AD

  • (c.) Maximus becomes bishop of Naples (to ~368).

360 AD

  • Huns begin invading Europe.
  • Codex-style books gradually replace scrolls.

361 AD

  • Earthquake hits Sicily; repeated disasters (famine, floods, quakes) plague Italy until 364, plus endemic plague to 394.
  • 285th Olympiad.
  • Constantius II dies, succeeded by cousin Julian (the Apostate).
  • Julian restores paganism and proclaims universal toleration.

362 AD

  • Julian’s further reforms anger Christians:
    • Rebuild Jewish Temple in Jerusalem, forbid Christian teaching of liberal arts, restore exiled bishops, and remove special privileges from Christians.
  • Sicily endures drought, famine, pestilence.

363 AD

  • (May 29) Julian is killed in Persia—likely assassinated by a Christian soldier.
  • Jovian, a Catholic, succeeds him. Jovian restores Christian privileges but also decrees universal toleration.

364 AD

  • (Feb 17) Jovian dies from suffocation.
  • Valentinian I is named emperor (Feb 28); associates brother Valens as Eastern Emperor.
  • Valentinian I is Catholic, tolerant of pagans; Valens is Arian, persecuting Catholics & pagans.
  • Both brothers despise scholars.
  • St. Cyprian, bishop of Brundisium, dies.

365 AD

  • 286th Olympiad.
  • St. Patricia founds a convent of Basilian nuns in Naples.
  • Q. Aurelius Symmachus becomes corrector (governor) of Lucania & Bruttium.

366 AD

  • Pope Liberius dies, succeeded by St. Damasus I.
  • A rival group elects Ursinus as antipope. Violent clashes ensue in Rome over the papal seat.

369 AD

  • 287th Olympiad.

373 AD

  • 288th Olympiad.

374 AD

  • Earthquake at Rhegium.
  • St. Ambrose becomes bishop of Milan, a major Christian figure of the late 4th century.

375 AD

  • (Nov 17) Valentinian I dies; his sons Gratian and Valentinian II divide the West.
  • Gratian refuses the pagan title Pontifex Maximus and adopts a harsher anti-pagan stance.
  • Earthquake at Beneventum.

376 AD

  • Q. Aurelius Symmachus is consul suffect and Praetorian Prefect in Italy.

377 AD

  • 289th Olympiad.

378 AD

  • Valens is defeated and killed by Goths at Adrianople—a catastrophic Roman loss.
  • Theodosius I becomes emperor in the East, enforcing Catholic orthodoxy and persecuting other sects.

379 AD

  • Volcanic activity at Vesuvius to ~395.

380 AD

  • (Feb 27) Theodosius I declares Christianity the official religion of the empire.

381 AD

  • 290th Olympiad.
  • Council of Constantinople reaffirms the Nicene Creed and grants the Bishop of Rome primacy.

382 AD

  • Pope Damasus I instructs St. Jerome to revise Latin Bibles, leading to the Vulgate.

383 AD

  • (Aug 15/25) Gratian is assassinated by Andragathius, a general of the usurper Magnus Maximus.

384 AD

  • Q. Aurelius Symmachus is Urban Prefect of Rome. He declines the usual pomp of office.
  • Rome begins military withdrawal from Britain.
  • St. Siricius becomes pope after Damasus I.
  • Jerome’s new Latin Gospels face criticism from Siricius.

385 AD

  • 291st Olympiad.

388 AD

  • Theodosius orders Christians to rebuild a Jewish synagogue they destroyed but retracts under threat from Bishop Ambrose.

389 AD

  • 292nd Olympiad.

390 AD

  • Theodosius punishes Thessalonika for revolt, massacring ~7,000 civilians.
  • Bishop Ambrose excommunicates him for 8 months.

391–392 AD

  • Theodosius issues edicts effectively banning paganism.
  • Pagan ceremonies persist in southern Italy and Sicily under a Christian veneer—superstitions like the mal occhio endure.
  • Synod at Capua debates leadership in the See of Antioch and heretic bishop Bonosus of Sardica.
  • Lapsed Christians returning to paganism are refused rebaptism or reordination.

392 AD

  • Emperor Valentinian II is murdered by Arbogast; the usurper Eugenius restores rights to pagans.

393 AD

  • 293rd Olympiad, the last official ancient Olympic Games.
  • Abundantius is consul of Rome.

394 AD

  • Eugenius is defeated and killed by Theodosius at the Battle of Frigidus.
  • Theodosius reimposes religious intolerance, banning pagan rituals, the Olympic Games, and Pythian Games.
  • He is the last sole ruler of the entire Roman Empire.

395 AD

  • (Jan 11 or 17) Theodosius I dies. The empire permanently splits:
    • Arcadius in the East,
    • Honorius in the West.
  • Both are strict Catholics.
  • Campanian farmland is abandoned (~330,000 acres), returning to swampland and fostering malaria outbreaks.

396 AD

  • Visigoths under Alaric sack Athens.

399 AD

  • Pope Anastasius I (St. Anastasius) succeeds Siricius (some sources date it 398).

Key Takeaways

  1. Imperial Reforms & Feudal Roots
    • Diocletian’s binding of peasants to the land foreshadows medieval feudalism.
    • Economic controls (price edict) and administrative reorganizations (prefectures, dioceses) profoundly shape governance.
  2. Rise & Legalization of Christianity
    • From the Great Persecution (303) to the Edict of Milan (313), then Theodosius’s declaration of Christianity as the state religion (380).
    • Pagans, Jews, and heterodox Christians faced severe restrictions.
    • Papal authority grows in Rome, with bishops gaining judicial privileges.
  3. Persecution & Pagan Suppression
    • Despite Constantine’s tolerance, later rulers (Constantius II, Theodosius) harshly suppress pagan temples and sacrifice.
    • The final edicts effectively outlaw pagan worship, though in rural areas older beliefs endure in disguised forms.
  4. Shifting Power Structures
    • Repeated civil wars: Maxentius vs. Constantine, Licinius vs. Constantine, usurpations under Magnentius and Eugenius.
    • The empire is frequently divided among co-emperors or Augusti, culminating in the permanent East-West split after Theodosius’s death (395).
  5. Cultural & Social Change
    • Construction of St. Peter’s in Rome, founding of Constantinople, and the first Christian councils (Nicaea, Constantinople) reshape religious doctrine.
    • Codex format gradually replaces scrolls, altering reading and record-keeping habits.

By the end of the 4th century AD, Christianity is dominant, paganism officially banned, and the empire firmly split between East and West. Recurrent invasions, economic woes, and social upheavals set the stage for the eventual dissolution of the Western Roman Empire in the following century.