Xu Guangqi 徐光啓 (1562-1633) seems to have asserted his famous slogan—“Melt the materials of that side, and incorporate them into the mould of Datong” (Rong bifang zhi caizhi, ru Datong zhi xingmo 鎔彼方之材質, 入大統之型模)―mainly to justify his accommodation of Western astronomical methods and knowledge to the Chongzhen 崇禎 calendar reform. Many later Confucian scholars quoted, modified, and commented on it, while coping with the problem of introducing Western astronomical knowledge and methods into the Chinese calendrical system. In this paper, I will look at the different ways they dealt with the slogan, which will illustrate the different attitudes they had towards various Western astronomical knowledge and methods, and their different views about the proper way to accommodate them in what they considered the “correct” calendrical method.