班固写的《汉书》上记载：“冬，民既入；妇人同巷，相从夜绩，女工一月得四十五日”。这几句读起来很奇怪，怎么一月能有四十五天呢？再看原文底下颜师古作了注解，他说：“一月之中，又得夜半十五日，共四十五日”。一个月本来只有三十天，古人把每个夜晚的时间算做半日；就 Class written in the “Han” on the record: “Winter, the people both; women with alley, phase from the night performance, female workers in January was 45 days.” These few words are very strange to read, how can we have 45 days in January? Look at the text of the original Yan Shi Gu made annotations, he said: “In January, another half-night 15 days, a total of 45 days.” There were only thirty days in a month, and the ancients counted half a day for each night