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The 320s

116 sourced entries across 10 years, inside the 4th century. Each year below opens its own page; the lines under it are that year’s highest-ranked entries.

320 CE24 entries

  • October 18 – Pappus of Alexandria, Greek philosopher, observes an eclipse of the sun and writes a commentary on The Great Astronomer (Almagest).
  • King Chandragupta I founds the Gupta dynasty in northern India (approximate date).
  • In Nydam Mose (Denmark), the Nydam oak boat is sacrificed by the Danes (the boat is excavated in the 1830s, when a local farmer finds weapons, including swords and spears).

321 CE13 entries

  • March 7 - Constantine I signs legislation directing urban residents to refrain from work, and businesses to be closed, on the "venerable day of the Sun". An exception is made for agriculture.
  • Constantine I assigns convicts to grind Rome's flour, in a move to hold back the rising price of food in an empire whose population has shrunk as a result of plague.
  • History of the Jews in Germany: Jews in modern-day Germany are documented for the first time, in Colonia Agrippinensium (modern-day Cologne).

322 CE7 entries

  • The first dependable representation of a horse rider with paired stirrups is found in China, in a Jin Dynasty tomb.

323 CE6 entries

  • Emperor Constantine the Great defeats the invading Goths and Sarmatians north of the Danube in Dacia, and claims the title of Sarmaticus Maximus.
  • Crown Prince Ming of Jin succeeds his father Yuan of Jin as emperor of the Eastern Jin Dynasty.

324 CE15 entries

  • July 3 – Battle of Adrianople: Emperor Constantine the Great defeats his rival Licinius near Adrianople, forcing him to retreat to Byzantium. Constantine then invades Thrace with a Visigothic force and raids the countryside.
  • August 9 – (guiyou day of the 7th month of the 2nd year of the Tai'ning era) In Jin dynasty China, the rebel warlord Wang Dun succumbs to illness as the armies of the Emperor Ming of Jin are approaching his camp.
  • September 18 – Battle of Chrysopolis: Constantine I definitively defeats Licinius at Chrysopolis, and becomes sole Emperor, thus ending the period of the Tetrarchy. Licinius escapes and gathers around 30,000 of his surviving troops at Nicomedia. Thus, the Civil wars of the Tetrarchy, which began in 306, end with Constantine ruling as sole Emperor.

325 CE13 entries

  • April 1 – Crown Prince Cheng of Jin, age 4, succeeds his father Ming of Jin as emperor of the Eastern Jin dynasty. During his reign, he is largely advised by regents, his uncle Yu Liang and high-level officials.
  • May 20 – First Council of Nicaea: Constantine summons an ecumenical council of bishops in Nicaea (Turkey). The Nicene Creed, adopted on June 19, declares that the members of the Trinity (the Father, the Son, and the Holy Spirit) are equal. The council decides that Easter is celebrated on the first Sunday after the first full moon after the vernal equinox. Arius is exiled to Illyria; his works are confiscated and consigned to the flames.
  • German and Sarmatian campaigns of Constantine: Emperor Constantine I personally assures the security of the Danube frontier by defeating the Goths, the Vandals and the Sarmatians.

326 CE11 entries

  • September 14 (traditional date) – Helena, mother of Constantine I, discovers the so-called True Cross and the Holy Sepulchre (Jesus's tomb) in Jerusalem. On her pilgrimage, which begins about this year, she pauses on the Aegean island of Patmos, where she is said to found the church of Panagia Ekatontapiliani.
  • Emperor Constantine the Great travels to Rome to celebrate the 20th anniversary of his accession to power, but while en route at Pola he orders his older son, Crispus Caesar, to be executed, possibly on charges of adultery. Later, Fausta, second wife of Constantine I, is also executed by being suffocated or boiled in a hot bath.
  • Helena tells Constantine that he must atone for executing his son and wife by building churches, and at about this date construction begins on Old St. Peter's Basilica, the first church on the traditional site of Saint Peter's tomb in Rome, and on the basilica of Golgotha on Calvary outside Jerusalem. He also commissions construction of the Church of the Nativity in Bethlehem (dedicated 339).

327 CE9 entries

  • Approximate traditional date – Helena, mother of Constantine, returning from her pilgrimage to the Holy Land, founds Stavrovouni Monastery on Cyprus.
  • Emperor Constantine the Great decrees that rural slaves can only be sold in the province where they reside, in order to resolve the shortage of labour in the Roman Empire.
  • Construction begins on the Great Church of Antioch, which will be completed in 341.

328 CE10 entries

  • May 9 – Athanasius is elected pope of Alexandria following the death of Alexander I.
  • July 5 – Constantine's Bridge, built over the Danube between Sucidava (Corabia, Romania) and Oescus (Gigen, Bulgaria), is officially opened by the Roman architect Theophilus Patricius.
  • December 7 – Lakhmid king Imru' al-Qays ibn 'Amr dies. His epitaph, the Namara inscription, is an important source for the Arabic Language.

329 CE8 entries

  • Roman restrictions on joining the clergy are initiated.
  • The Han-Zhao dynasty, a Southern Xiongnu state during the Sixteen Kingdoms, ends.