In the early Joseon Dynasty, there were several kinds of example supplements (假令) including the calculation methods and results of the solar and lunar eclipses that happened in August of Jeongmyonien (丁卯年, 1447). Among them, this paper discusses the Chijongsan-Napion Jeongmyonien Kyosik-Garyong (七政算內篇丁卯年交食假令) and the Kyosikchubobub-Garyong (交食推步法假令) published in 1444 and 1458, respectively.
According to the comparative study of these two versions, the newly revised calculation method of the solar and lunar eclipse was introduced from China after the compilation of the Chiljongsan-Napion (七政算內篇), and it was studied and revised by King Sejong and the court astronomers of Joseon (朝鮮). Later , it was published by the order of King Sejo with the title of the Kyosikchubobub-Garyong. This edition shows that there was a reform of the calender system after the Datonglifa-Tonggui (大統曆法通軌) in Ming(明) Dynasty. Therefore, we have examined the solar and lunar eclipsing methods used in the early Joseon Dynasty and the process of their revision. In addition, we analysed the calculation method of the addition and subtraction difference (加減差) used in the calculation of true positions of the sun and the moon, which is the main difference between the two. As a result, it is revealed that the main factor of prediction errors came from the time of real new moon and full moon obtained from the calculation of the addition and subtraction difference.