Japan has been ruled by emperors since antiquity. The sequence, order and dates of the early emperors are almost entirely based on the 8th-century Nihon Shoki, which was meant to retroactively legitimise the Imperial House by dating its foundation further back to the year 660 BC.[1][2][3] There are several theories as to who was the first Japanese ruler supported by historical evidence: notable candidates are Emperor Yūryaku (r. 456–479) and Emperor Kinmei (r. 539–571), among others.[4][5]
The terms Tennō ('Emperor', 天皇), as well as Nihon ('Japan', 日本), were not adopted until the late 7th century AD.[6][2] In the nengō system which has been in use since the late 7th century, years are numbered using the Japanese era name and the number of years which have elapsed since the start of that nengō era.[7]
Timothy
was invoked but never defined (see the help page).