400

By place

Roman Empire

• January 9 – Emperor Arcadius gives his wife Aelia Eudoxia the official title of Augusta. She is able to wear the purple paludamentum and is depicted in Roman currency.
• Anthemius, praetorian prefect of the East, is sent on an embassy to the Persian capital, Ctesiphon, to congratulate King Yazdegerd I on his accession the year before.
• A riot breaks out in Constantinople; the Great Palace is burned to the ground. Gainas, a Gothic leader, attempts to evacuate his soldiers out of the city, but 7,000 armed Goths are trapped and killed by order of Arcadius. After the massacre, Gainas tries to escape across the Hellespont, but his rag-tag ad hoc fleet is destroyed by Fravitta, a Gothic chieftain in imperial service.
• Winter – Gainas leads the remaining Goths back to their homeland across the Danube. They meet the Huns and are defeated; the Hunnic chieftain Uldin sends the head of Gainas to Constantinople, where Arcadius receives it as a diplomatic gift.

  Europe

• The Franks establish themselves in the North of the Netherlands.
• The Paeonians lose their identity.
• The Vandals start their westward trek from Dacia and Hungary.

  Asia

• Chrysanthemums are introduced into Japan.
• Richū, the eldest son of Nintoku, becomes the 17th Emperor of Japan.

  By topic

Art

• Resurrection and "Two Marys with Angel near the Empty Tomb", panel of a diptych, found in Rome, is made. It is now kept at Castello Sforzesco, Milan.

  Literature

• The Vergilius Vaticanus, an illuminated manuscript containing fragments of Virgil's Aeneid and Georgics, is made in Rome.
• The Yoga Sutras of Patanjali are composed.

  Medicine

• Caelius Aurelianus, Roman physician, is practising his work "De morbis acutis et chronicis", a guide to acute and chronic diseases.

  Physics

• Hypatia, Greek philosopher, distinguishes herself as one of the first women scientists, and becoming head of the Neo-Platonist school at Alexandria.

  Religion

• The mausoleum of Galerius in Salonica is converted into a church.
• Bishops from Gaza arrive at Constantinople to ask Arcadius that he close the pagan temple at Marneum.