《元史·列传·卷五十一》
又上《合朔议》，陈述自秦以来修改历法的经过，最后说： 臣等更造新历，是依据过去历法家们的定论，考察观测天象的运行情况，自至元十九年八月后，完全符合日月运行的日数。 
详见《郭守敬传》。是日，方列跪，未读奏，帝命许衡及恭懿起，曰： 卿二老，毋自劳也。 
He also submitted a "He Shuo Yi", stating the process of revising the calendar since the Qin Dynasty, and finally said: My colleagues and I have created a new calendar based on the established theories of past calendar makers, and observed the運行 of celestial phenomena, starting from August 19th year of the Yuan Dynasty, which completely matches the number of days of the sun and moon's運行. 