Ninna (仁和?) was a Japanese era name (年号,, nengō,?, lit. "year name") after Gangyō and before Kanpyō. This period spanned the years from February 885 through April 889. The reigning emperors were Kōkō-tennō (光孝天皇?) and Uda-tennō (宇多天皇?).
Read more about Ninna: Change of Era, Events of The Ninna Era