Ten'an (天安) was a Japanese era name (年号,, nengō,; lit. "year name") after Saikō and before Jōgan. This period started in February 857 and ended in April 859. During this time, the emperors were Montoku-tennō (文徳天皇) and Seiwa-tennō (清和天皇).
Events of the Ten'an era
In Ten'an 2, the start of Seiwa's reign was announced at Kotai-jinju in Ise
27 September 858 (Ten'an 2, 27th day of the 8th month): Emperor Montoku dies; and the succession (senso) was received by his eldest son. Emperor Seiwa accepted the monarch's role and duties and powers (sokui). This was confirmed in ceremonies. The start of Seiwa's reign was announced at the Ise Shrine (Kotai-jingu) at Ise and at all the tombs of the imperial family.
15 December 858 (Ten'an 2, 7th day of the 11th month): The emperor's grandfather is named regent (sesshō).
♯The Northern pretenders did not recognize the Genkō era. Gentoku was used in the Northern Court until 1332. ₪The Shōkyō era was recognized only by the Northern pretenders, not by the Southern Court. ‡ Upon reunification of the Northern and Southern Courts in 1392, Genchū was discontinued. Meitoku was used until 1394.