置周天三百六十五日二十五分，以二十七日除之，每日得一十三度，余有一十四度二十五分。
以约法相减，（以二十七减十四度二十五分。）得七十五停，相减停也。三次相减停，以七十五
为法，先除母二十七日，乃二千七百也。除之得母，（三十六为母也。）以七十五除子一十四度
二十五分，得一十九也，故三十六分度之一十九。一日一十三度三十六分度之一十九，二日二十
七度三十六分之二，三日四十度三十六分度之二十一，四日五十四度三十六分度之四，五日六十
七度三十六分度之二十三，六日八十一度三十六分度之六，七日九十四度三十六分度之二十五。
直候加至二十七日，乃得三百六十五度三十六分度之九也，故二十七日合周天三百六十五日四分
度之一也。度之一者，乃一百刻中得二十
五，四个二十五也，乃百刻也。共合之今法，以三十六分为母，以合三百六十五度三十六分度之
九，故四个九，亦三十六也，合四分度之一也。
（新添）当六岁也，自余岁外之法。别有三百五十四日，而为一岁，通少一十一日五十五
刻，乃积气余而盈闰也。凡闰之月，无中气，皆是前后三辰之分也，乃天度之数也。其象应期而
有圆缺者，月象非有缺也。然月为太阴，水之精也，日象太阳，火之精也，日月相见，则为明字，
乃天之道也。火为阳明之于外，水为阴明之于内，以火大彰，以水鉴形，而可形之也。目之见也，
同其太阳，照而象方见也。日光不能照者，其象不彰而缺也，以视其象，而可狂也。故上弦月南，
则日乃西见而下之半也，下弦月南，则日乃东见而上之半也，望则日月相对，是故圆明，晦则同
宫，是故视之不见矣。又如，冰虽莹，夜悬暗室，非火炳明，而岂鲜见其形矣。是知冰虽内明，
非明曜而形无所见，月虽中朗，非日辉其象不能彰。是故月本无缺，盖因日月行之迟速不等，而
故有盈亏矣。
将周天度数三百六十五度二十五分，用二十七天去除它，每天得到十三度，余下十四度二十五分。
用约分法相减（用二十七减去十四度二十五分），得到七十五份，这是相减后的份数。三次相减后取整，以七十五为除数，先除被除数的整数部分二十七天，即二千七百。再除得整数部分（三十六为分母）。用七十五去除分子十四度二十五分，得到十九，所以是三十六分之十九。第一天行十三度又三十六分之十九，第二天行二十七度又三十六分之二，第三天行四十度又三十六分之二十一，第四天行五十四度又三十六分之四，第五天行六十七度又三十六分之二十三，第六天行八十一度又三十六分之六，第七天行九十四度又三十六分之二十五。
一直累加到二十七天，就得到三百六十五度又三十六分之九，所以二十七天合周天三百六十五度又四分之一度。四分之一度，即在百刻中得到二十五刻，四个二十五刻就是一百刻。按现行方法合并计算，以三十六分为分母，与三百六十五度又三十六分之九相加，所以四个九也是三十六，合起来就是四分之一度。
（新添）当逢六年时，有从历年累积而来的算法。另有三百五十四日作为一年，总共少一十一日五十五刻，这是积气有余而设置闰月的结果。凡是闰月，没有中气，都是前后三个时辰的分界，这是天体运行的度数。月亮形象随着周期而有圆缺变化，但月亮本身并没有缺损。然而月亮属太阴，是水的精华；太阳属太阳，是火的精华。日月相见，组成“明”字，这是天道的体现。火代表阳明在外，水代表阴明在内，用火来彰显，用水来映照形体，从而可以显现形状。眼睛看见事物，如同太阳照耀，光照则形象显现。日光不能照到的地方，形象不显而显得残缺，观察其形象，就可以理解这种盈亏现象。所以上弦月在南天时，太阳在西边落下的一半；下弦月在南天时，太阳在东边升起的一半；满月时日月相对，所以圆满明亮；晦日时日月同宫，所以看不见月亮。又如，冰虽然晶莹，夜晚悬挂在暗室中，如果没有火把照明，怎么能清楚地看到它的形状呢？由此可知，冰虽然内部明亮，但没有光亮照射就看不到形状；月亮虽然中间朗照，但没有日辉照耀，其形象也不能显现。所以月亮本来没有缺损，只是因为日月运行速度不等，所以才有了盈亏变化。
Set the celestial sphere at 365 degrees and 25 fen. Divide by 27 days; each day yields 13 degrees, with a remainder of 14 degrees and 25 fen.
Using the reduction method for subtraction (subtracting 14 degrees and 25 fen from 27), we obtain 75 parts, which represents the result after subtraction. After performing this subtraction three times to normalize, take 75 as the divisor. First, divide the integer part of the dividend, 27 days, multiplied by 100, yielding 2700. Then divide to get the integer part (where 36 serves as the denominator). Divide the numerator, 14 degrees and 25 fen, by 75, obtaining 19. Thus, it is 19/36. On the first day, the moon travels 13 degrees and 19/36; on the second day, 27 degrees and 2/36; on the third day, 40 degrees and 21/36; on the fourth day, 54 degrees and 4/36; on the fifth day, 67 degrees and 23/36; on the sixth day, 81 degrees and 6/36; on the seventh day, 94 degrees and 25/36.
Continuing this accumulation until the twenty-seventh day, one arrives at 365 degrees and 9/36. Therefore, 27 days correspond to the celestial sphere of 365 degrees and 1/4 degree. One-quarter degree corresponds to 25 ke within 100 ke; four sets of 25 ke make up 100 ke. According to the current combined calculation method, using 36 as the denominator, adding to 365 degrees and 9/36, four nines equal 36, thus combining to form one-quarter degree.
(New addition) In the case of the sixth year, there is a method derived from accumulated years. There are alternatively 354 days constituting one year, totaling 11 days and 55 ke less, which accounts for the surplus of accumulated Qi leading to intercalary months. Any intercalary month lacks a Zhongqi (Central Qi); these are all divisions of the preceding and following three Chen (two-hour periods), representing the numerical value of celestial degrees. The lunar image appears full or deficient according to its cycle, but the Moon itself does not actually lack substance. The Moon belongs to Taiyin (Greater Yin) and is the essence of Water; the Sun belongs to Taiyang (Greater Yang) and is the essence of Fire. When the Sun and Moon meet, they form the character "Ming" (Brightness), which embodies the Way of Heaven. Fire represents Yangming (Bright Yang) on the outside, and Water represents Yinming (Bright Yin) on the inside. Using Fire to illuminate and Water to reflect shapes allows their forms to be perceived. Vision in the eye is similar to the Sun shining; where light shines, images appear. Where sunlight cannot reach, images do not manifest and appear deficient; observing these images allows one to understand the phenomenon. Thus, when the waxing half-moon is in the south, the Sun is seen in the west setting in its lower half; when the waning half-moon is in the south, the Sun is seen in the east rising in its upper half. At Full Moon, the Sun and Moon face each other, resulting in a round and bright appearance. At New Moon, they share the same palace, making them invisible to the eye. Furthermore, although ice is translucent, if hung in a dark room at night without a torch providing light, how could its shape be clearly seen? From this, we know that although ice has internal brightness, without external illumination, its form cannot be seen; although the Moon shines internally, without the radiance of the Sun, its image cannot be manifested. Therefore, the Moon originally has no deficiency; it is merely due to the unequal speeds of the Sun and Moon's movements that the phases of waxing and waning occur.