《明史·志·卷七》
又说月份和十二辰的对应与北斗斗柄的指向没有关系，北斗斗柄所指有岁差，而月份和十二辰的对应没有变动。
又月建月关半杓所指，斗杓有岁差，而月建无改移。
It is also said that the correspondence between months and twelve shichen has nothing to do with the direction of the handle of the Big Dipper. The direction of the handle of the Big Dipper has a precession of the equinoxes, while the correspondence between months and twelve shichen does not change.