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671Jun, 10
Emperor Tenji of Japan introduces a water clock (clepsydra) called Rokoku. The instrument, which measures time and indicates hours, is placed in the capital of Ōtsu.
Emperor Tenji (天智天皇, Tenji-tennō, 626 – January 7, 672), also known as Emperor Tenchi, was the 38th emperor of Japan, according to the traditional order of succession.Tenji's reign spanned the years from 661 through 672.