 The Chinese calendar was in need of reform since it inadequately measured the solar year at 365 ¼ days , giving an error of 10 min and 14 sec a year or roughly a full day every 128 years . Although the Ming had adopted Guo Shoujing 's Shoushi calendar of 1281 , which was just as accurate as the Gregorian Calendar , the Ming Directorate of Astronomy failed to periodically readjust it ; this was perhaps due to their lack of expertise since their offices had become hereditary in the Ming and the Statutes of the Ming prohibited private involvement in astronomy . A sixth @-@ generation descendant of the Hongxi Emperor , the " Prince " Zhu Zaiyu ( 1536 – 611 ) , submitted a proposal to fix the calendar in 1595 , but the ultra @-@ conservative astronomical commission rejected it . This was the same Zhu Zaiyu who discovered the system of tuning known as equal temperament , a discovery made simultaneously by Simon Stevin ( 1548 – 1620 ) in Europe . In addition to publishing his works on music , he was able to publish his findings on the calendar in 1597 . A year earlier , the memorial of Xing Yunlu suggesting a calendar improvement was rejected by the Supervisor of the Astronomical Bureau due to the law banning private practice of astronomy ; Xing would later serve with Xu Guangqi in reforming the calendar ( Chinese : 崇禎暦書 ) in 1629 according to Western standards . 
