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|Centuries:||3rd century – 4th century – 5th century|
|Decades:||290s 300s 310s – 320s – 330s 340s 350s|
|Years:||317 318 319 – 320 – 321 322 323|
|320 by topic|
|State leaders – Sovereign states|
|Birth and death categories|
|Births – Deaths|
|Establishment and disestablishment categories|
|Establishments – Disestablishments|
|Ab urbe condita||1073|
|Chinese calendar||己卯年 (Earth Rabbit)
3016 or 2956
— to —
庚辰年 (Metal Dragon)
3017 or 2957
|- Vikram Samvat||376–377|
|- Shaka Samvat||242–243|
|- Kali Yuga||3421–3422|
|Iranian calendar||302 BP – 301 BP|
|Islamic calendar||311 BH – 310 BH|
|Minguo calendar||1592 before ROC
|Seleucid era||631/632 AG|
|Thai solar calendar||862–863|
Year 320 (CCCXX) was a leap year starting on Friday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Constantinus and Constantinus (or, less frequently, year 1073 Ab urbe condita). The denomination 320 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.
- Crispus, eldest son of Constantine I, leads a victorious campaign against the Franks, assuring twenty years of peace along the Rhine frontier. He established his residence in Augusta Treverorum (modern Trier), capital of Germania.
- Licinius reneged on the religious freedom promised by the Edict of Milan, and begins a new persecution of Christians in the Eastern Roman Empire. He imprisons Christians, confiscates their properties and destroys churches.
- King Chandragupta I founds the Gupta dynasty in northern India.
- The Huns appear in Persia.
- Zhang Shi (張寔), Zhang Duke of Xiping and governor of Liang Province (涼州)is assassinated by Yan She (閻涉) and Zhao Ang (趙卬) and replaced by Zhang Mao (張茂), commonly accepted first ruler of the Chinese state Former Liang.
Culture and Religion
- 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.
- December 25 is introduced as the birthday of Jesus.
- October 18 – Pappus of Alexandria, Greek philosopher, observes an eclipse of the sun and writes a commentary on The Great Astronomer (Almagest).
- Aurelius Victor, historian and politician (approximate date)
- Constans I, Roman emperor (d. 350)
- Flavian I, Patriarch of Antioch (d. 404)
- Jin Jianwendi, emperor of the Jin Dynasty (d. 372)
- Oribasius, Greek physician (approximate date)
- Tuoba Shiyijian, prince of the Tuoba Dai (d. 376)
- Xie An, statesman of the Jin Dynasty (d. 385)
- Lactantius, Christian writer (approximate date)
- Sima Bao, prince of the Jin Dynasty (b. 294)
- Zhang Shi, Duke of Xiping