Jōkyō calendar  The was a Japanese lunisolar calendar, in use from 1684 to 1753. It was officially adopted in 1685. The "Jōkyō-reki" system was developed and explained by Shibukawa Shunkai. He recognized that the length of the solar year is 365.2417 days. Shibukawa discovered errors in the traditional Chinese calendar, the "Senmyō" calendar, which had been in use for 800 years.