Jōkyō calendar facts for kids
The Jōkyō-reki system was the work of Shibukawa Shunkai. He recognized that the length of the solar year is 365.2417 days.
Shirakawa discovered errors in the traditional Chinese calendar which had been in use for 800 years. This older system was also known as the Semmyō calendar or 'Semmei-reki. It was also known as the Xuanming calendar.
Jōkyō calendar Facts for Kids. Kiddle Encyclopedia.