Kōka

Kōka (弘化?) was a Japanese era name (年号,, nengō,?, lit. "year name") after Tenpō and before Kaei. This period spanned the years from December 1844 through February 1848. The reigning emperors were Ninkō-tennō (仁孝天皇?) and Kōmei-tennō (孝明天皇?).

Read more about Kōka:  Change of Era, Events of The Kōka Era