《黄帝内经·素问·六微旨大论》
岐伯说：所谓 步 ，就是指六十度有零的时间，每年是六步，所以在二十四步中，也就是四年内，积每年刻度的余数共为一百刻，就成为一日。
岐伯曰：所谓步者，六十度而有奇，故二十四步，积盈百刻而成日也。
Qi Bo said: The so-called 步 (bu) refers to the time span of sixty minutes. There are six 步 (bu) in a year, therefore, in twenty-four 步 (bu), namely four years, the accumulated remainder of the time span of each year equals one hundred time units, which becomes a day.