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Year 355 (CCCLV) was a common year starting on Sunday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Arbitio and Maesius (or, less frequently, year 1108 Ab urbe condita). The denomination 355 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.
|Ab urbe condita||1108|
|Balinese saka calendar||276–277|
|Chinese calendar||甲寅年 (Wood Tiger)|
3051 or 2991
— to —
乙卯年 (Wood Rabbit)
3052 or 2992
|- Vikram Samvat||411–412|
|- Shaka Samvat||276–277|
|- Kali Yuga||3455–3456|
|Iranian calendar||267 BP – 266 BP|
|Islamic calendar||275 BH – 274 BH|
|Minguo calendar||1557 before ROC|
|Seleucid era||666/667 AG|
|Thai solar calendar||897–898|
481 or 100 or −672
— to —
482 or 101 or −671
- January 1 – Arbitio and Lollianus Mavortius begin their term as Roman consuls.
- August 11 – Claudius Silvanus, accused of treason, proclaims himself Roman Emperor. After 28 days, Ursicinus arrives from Rome and has Silvanus murdered.
- November 6 – In Mediolanum (Italy), Emperor Constantius II raises his cousin Julian the Apostate to the rank of Caesar. He takes command of the western provinces and marries Constantius' sister, Helena.
- The Lentienses, a Germanic tribe, are fined by the Roman commander Arbetio under Constantius II for several incursions against the Roman Empire.
- The Franks besiege Colonia Agrippinensium for ten months.
- The Huns of Central Asia begin their great drive westwards with an advance into Scythia (modern Russia). They overcome and absorb the Alans, a nomadic and warlike horse breeding people from the steppes northeast of the Black Sea.
- September 7 – Claudius Silvanus, Roman usurper
- Aedesius, Roman Neoplatonist philosopher and mystic
- Fu Jian, Chinese emperor of the Former Qin (b. 317)
- Liang, Chinese empress of the Former Qin Dynasty
- Zhang Yaoling, Chinese ruler of Former Liang (b. 344)
- Zhang Zuo (or Taibo), Chinese ruler of Former Liang
- E.J. Bickerman, Chronology of the Ancient World (Ithaca: Cornell University Press, 1968), p. 64
- Timothy David Barnes (1981). Constantine and Eusebius. Harvard University Press. p. 399. ISBN 978-0-674-16531-1.
- Ammianus Marcellinus, History, 15.2.3.
- Henry Fynes Clinton (1845). Fasti Romani: Tables. University Press. pp. 363.
- Jennifer Holmgren (1982). Annals of Tai: Early T'O-Pa History According to the First Chapter of the Wei-Shu. Faculty of Asian Studies. p. 91. ISBN 978-0-909879-16-7.