We should say a little about why calendar reform was such a frequent event in China while in Europe there has only been one major reform of the calendar. In ancient China there was a belief that a ruler received his right to rule from heaven. Changing the calendar was seen as one of the duties of the office, establishing the emperor's heavenly link on earth. After a change of ruler, and even more significantly after a change of dynasty, the new Chinese emperor would seek a new official calendar thus establishing a new rule with new celestial influences.
Luoxia Hong was one of the astronomers who went to Chang'an in answer to Emperor Wu-ti's request. Some of the astronomers were already part of Wu-ti's civil service, being imperial astronomers. Luoxia, however, lived in the southwest of China. Emperor Wu-ti received eighteen proposals for a new calendar, and he judged the best one was that received from Luoxia Hong and one of his colleagues Deng Ping. In 104 BC the calendar was put into operation by the Emperor.
There were 12 months of 29 or 30 days and the calendar was based on a cycle of 19 years. In seven of the 19 years an extra month was inserted making it a calendar based both on the sun and on the moon. Luoxia Hong's calendar was much more than simply an attempt to bring the sun and moon into a common system for he also gave predictions for the positions of the planets and predictions of eclipses. All this was only possible with good observations and the reason that they were good is that Luoxia Hong made an equatorial armillary sphere to make observations for his new calendar.
Emperor Wu-ti was delighted with Luoxia Hong's achievements and offered him an official position in Chang'an. This offer, however, was refused, and Luoxia Hong returned to live a solitary life.
Article by: J J O'Connor and E F Robertson