Jōgan

Jōgan (貞観) was a Japanese era name (年号, nengō, "year name") after Ten'an and before Gangyō.

This period spanned the years from April 859 through April 878.

[1] The two reigning emperors were Seiwa-tennō (清和天皇) and Yōzei-tennō (陽成天皇).

[2]