The Western Roman Emperor Constans campaigns in Britain against the Picts.
Constans campaigns victoriously against the Franks.
The senate abolishes gay marriage.
Year 342 (CCCXLII) was a common 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 Constantius and Claudius (or, less frequently, year 1095 Ab urbe condita). The denomination 342 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.
EuropeA large earthquake strikes Cyprus.
Goguryeo is invaded by Murong Huang of the Xianbei.
Jin Kangdi succeeds his brother Jin Chengdi as emperor of China.
Paul I, Patriarch of Constantinople, is deposed and replaced by Macedonius I.
February 15 – The original Hagia Sophia is dedicated in Constantinople.
Jin Feidi, emperor of the Eastern Jin Dynasty (d. 386)
July 26 – Jin Chengdi, emperor of the Jin Dynasty (b. 321)
Paul of Thebes, Christian hermit (approximate date)