The lunar-ecliptic-limit calculation of Chinese ancient calendar remains a largely untrodden field in present research. Therefore, this paper, through the calculations adopted by Hui Dong in his Guaqi theory in Yi Han Studies, aims to open a possible space for negotiation among different disciplines. In the following, I will discuss: 1) Examples of using Gua, or divinatory symbols, to decide the appropriateness of a certain daily-life activities, such as marriage or traveling, in Gan Xiang Calendar and Zheng Guang Calendar during both the second year of the Wu Huang Wu period and the first year of Northern Wei Yong-an Dynasty respectively. 2) Instances of adopting Gauqi in Da Yan Calendar in the first year of Tang Tian-bao Dyansty. 3) According the constants and calculation which appear in the combination of the Gauqi and Calendar during the first year of Tang Tian-bao Dyansty, one is able to figure out the then twenty-four Jieqi (season's qi), the appropriateness of conducting certain activities on certain days using Yi Gua, the seventy-two weather terms, the five fundamental elements (gold, wood, water, fire, and earth), and the period of divergent and convergent. Further, Guaqi theory enables one to forecast the weather, to explain and interpret the evolvement of Guaqi calendar in the Tang and Song Dynasties. Finally, the paper concludes that while Guaqi may have little or no use for the calculation of calendar, Hui Dong's Yi Han Studies contributes to the study of Yi Jing, or The Book of Changes.