For the machine-struck coinage of Japan (1870 to date), the dating of the coinage has been for the most part based off the reigning year of the emperor. Beginning with the coinage of 1870, the date that was stamped on the coins was the Japanese character combination for Meiji (enlightened peace), denoting Emperor Mutsuhito. Emperor Mutsuhito began his reign in 1868 and the first machine-struck coinage started in 1870 with year three appearing on the coin, signifying the commencement of the Mutsuhito reign. When Mutsuhito passed in 1912 it was the 45th year of his reign, thus ending the Meiji coinage. The dating then returned to year one with the character for Taisho (great righteousness) appearing upon commencement of the reign of Emperor Yoshihito.
Emperor Yoshihito year one equates to 1912, as it was the first year of his reign, and that dating system continued until 1926. After Yoshihito, coinage dates were reset again with the characters for Showa (enlightened peace) designating the commencement of the reign of Emperor Hirohito. Hirohito’s year one was 1926, and that dating convention continued until year 63, which was 1989. The Japanese characters Heisei (achieving peace) for Emperor Akihito started again with year one in 1989 and continue to 2019.
For the Japanese Occupation Coinage of World War II, a different dating system and dates appear on the coinage. The Japanese Shinto Dynastic Calendar starts with the year zero, equating to 660 BCE – this is the year Japan is believed to have been founded. For the coinage struck by the Osaka Mint for use in the East Indies under Japanese occupation, the dates 2603 and 2604 were used and equate to 1943 and 1944 in the Common Era calendar.
Japanese dating for coinage is very straightforward as long as the characters are read correctly.