《宋书·志·卷十六》
从束晋以来，都用正月，当是《春秋》传裹所说的夏、商、周的郊祀，全都用正月，晋代不改正朔，实行夏历，因此安排在年初，不用冬曰，全都用上旬的辛曰，这是近代的成规。
江左以来，皆用正月，当以传云三王之郊，各以其正，晋不改正朔，行夏之时，故因以首岁，不以冬日，皆用上辛，近代成典也。
Since the Eastern Jin Dynasty, the first month of the year has been used. It should be the suburban sacrifices of Xia, Shang, and Zhou mentioned in the "Chunqiu" legend. All of them are used in the first month of the year. The Jin Dynasty did not reform the first day of the year and implemented the Xia calendar, so it was arranged at the beginning of the year. It was not used on the winter day, and all of them were used on the Xinri of the first ten days. This is a modern rule.