《三国志·魏书·少帝纪》
又因为夏历正月从天数上是承袭天道，符合自然运转规律的，所以以夏历建寅之月即第一个月为正始元年的岁首，以建丑之月及第十二个月为岁末。 
又夏正於数为得天正，其以建寅之月为正始元年正月，以建丑月为后十二月。 
Also because the first month of the Chinese lunar calendar is inherited from the way of heaven in terms of the number of days, and it conforms to the laws of natural operation, therefore the month of Jian Yin of the Chinese Lunar Calendar, which is the first month, is the beginning of the first year, and the month of Jian Chou, which is the twelfth month, is the end of the year.