\r二十四向八刻二十分图\pt13a7.bmp\r
每日十二时，每时得八刻二十分，每刻分为六十分。分八刻为前后，则前四刻为初四刻，后四刻为正四
刻。分二十分为前后，则前十分为初初刻，后十分为正初刻。二十分者，即每刻六十分之二十也。
\r每日气数百刻六千分图\pt13a8.bmp\r
按周礼总义，每刻分为六十分，正合天元纪大论所谓天以六为节也。今遵此数推衍
之，则每日百刻，总计六千分。分六千分为十二时，则每时各得五百分。又分百刻于十二
时，则每时各得八刻二十分。总计岁有六步二十四气，则每气得十五日二时五刻十二分
半。计数得九万一千三百一十二分半。积四气而成步，则每步得六十日十时四刻一十分，计数得三十
六万五千二百五十分，即六微旨大论所谓六十日八十七刻半者是也。又积六步而成岁，则每岁得三百六十
五日二十五刻，计数得二百一十九万一千五百分，乃为一岁之定数。然以每月三十日计之，则每岁止
三百六十日，又除小月六日，则止三百五十四日，共少于前数者十一日。乃积余日，大约六十五气有零，
当得一闰，统十九年以成七闰，而岁气成矣。故六节藏象论曰∶大小月三百六十五日而成岁，
积气余而盈闰矣。（六节藏象论义，详运气类第一章。）
\r二十四气昼夜长短百刻之图\pt13a9.bmp\r
[Diagram of Twenty-Four Directions, Eight Ke and Twenty Fen]
There are twelve double-hours (Shichen) in a day. Each double-hour comprises eight *ke* (traditional time units) and twenty *fen* (sub-units). Each *ke* is divided into sixty *fen*. Dividing one *ke* into front and back halves, the first four *ke* are called "Chu Si Ke" (Initial Four Ke), and the latter four *ke* are called "Zheng Si Ke" (Regular Four Ke). Dividing the twenty *fen* into front and back halves, the first ten *fen* are called "Chu Chu Ke" (Initial Initial Ke), and the latter ten *fen* are called "Zheng Chu Ke" (Regular Initial Ke). These twenty *fen* refer to twenty parts out of the sixty *fen* constituting one *ke*.
[Diagram of Daily Qi, One Hundred Ke, Six Thousand Fen]
According to the general principles of the *Rites of Zhou* (Zhou Li), dividing each *ke* into sixty *fen* perfectly aligns with the statement in the *Tianyuan Ji Dalun* (Great Treatise on the Heavenly Origin) that "Heaven uses six as its rhythm." Following this numerical system for deduction: a day consists of one hundred *ke*, totaling six thousand *fen*. Distributing these six thousand *fen* among the twelve double-hours yields five hundred *fen* per double-hour. Similarly, distributing one hundred *ke* among the twelve double-hours yields eight *ke* and twenty *fen* per double-hour. In total, there are six steps (Liu Bu) and twenty-four solar terms (Er Shi Si Qi) in a year. Thus, each solar term corresponds to 15 days, 2 double-hours, 5 *ke*, and 12.5 *fen*. The cumulative count amounts to 91,312.5 *fen*. Accumulating four solar terms constitutes one step; thus, each step comprises 60 days, 10 double-hours, 4 *ke*, and 10 *fen*, totaling 365,250 *fen*. This corresponds to the statement in the *Liuzhi Da Lun* (Great Treatise on the Six Micro-Directions) regarding "eighty-seven and a half *ke* in sixty days." Accumulating six steps forms a year, resulting in 365 days and 25 *ke* per year, which totals 2,191,050 *fen*, representing the fixed number for a year. However, calculating based on thirty days per month yields only 360 days per year. Subtracting the six days missing from small months leaves 354 days, which is eleven days fewer than the aforementioned figure. Therefore, by accumulating the surplus days, after approximately more than sixty-five solar terms, a leap month should be established. By integrating nineteen years to form seven leap months, the cycle of yearly Qi is completed. Hence, the *Liu Jie Zang Xiang Lun* (Treatise on the Six Sections and Visceral Manifestations) states: "Large and small months combined amount to three hundred sixty-five days to form a year; accumulating the surplus of Qi results in intercalation." (For the interpretation of the *Liu Jie Zang Xiang Lun*, see Chapter 1 of the Yun Qi category.)
[Diagram of Day and Night Lengths for Twenty-Four Solar Terms in One Hundred Ke]