Datong Calendar for the 25th Year of the Yongli Reign (1671)

Photo source: Bodleian Library Sinica 58

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Note: The images shown below have been cropped and resized from the originals. Only a few pages containing the information of conjunctions, intercalary months and solar terms are shown here. The digital version of the whole book can be obtained from the source link above.

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Text

大 明 中 興 永 曆 二 十 五 年 大 統 曆

嗣藩 頒製

皇曆遙頒未至本藩權宜命官依

  大統曆法考正刊行俾

中興臣子咸知

正朔海內士民均沾厥福用是為識

Translation

The book title is Datong Calendar for the Twenty-Fifth Year of the Yongli Reign in the Great Ming Dynasty.

The text roughly states that the emperor's calendar for the year had not arrived and the Prince of Yanping (governor of the Zheng state) expediently ordered officials to produce and promulgate the calendar according to the Datong system, so that the civilians under his governance could use it for their daily lives.

Note: The emperor's calendar of the Southern Ming dynasty was no longer produced after the death of the Youngli emperor in 1662. This calendar became the de facto official calendar of the state.

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Translation

Column Description

1. The first column is the Chinese month number followed by either S (short month) or L (long month). The S months had 29 days and L months had 30 days. The total number of days in the year was therefore 30N_L + 29N_S, where N_L is the number of L months and N_S is the number of S months. The calculated number matches the value given in the last row of the table.
2. The second column gives the sexagenary date cycle of the first day (conjunction day) in the Chinese month.
3. The last two columns list the dates and times of the solar terms in the year.
   • Solar terms are labelled using the convention on the solar term page. They are shorthand notations of the alternative Chinese names. For example, Z5 refers to the Zhongqi (major solar term) associated with month 5 (五月中), which is Summer Solstice (夏至); J6 refers to the Jieqi (minor solar term) associated with month 6 (六月節), which is Slight Heat (小暑).
   • The date of a solar term is given by a number indicating the date in the Chinese month and the sexagenary date cycle. For example, "J2: 26, Ji Mao" means that J2 was on the 26th day (of month 1) and its sexagenary date cycle was Ji Mao.
   • Time is indicated by two numbers (x,y), where x is an integer between 0 and 23 and y is an integer between 0 and 4. If y≠4, (x,y) means that the time is between 14.4y minutes and 14.4(y+1) minutes past x o'clock. If y=4, (x,y) means that the time is between 57.6 minutes past x o'clock and (x+1) o'clock. For exampe, (20,3) refers to the time interval between 20:43:12 and 20:57:36; (2,4) refers to the time interval between 2:57:36 and 3:00:00.
   • Hence, "J10: 5, Gui Wei, (5,1)" in the 10S row means that J10 occurred in the time interval between 5:14:24 and 5:28:48 on the 5th day of month 10 and the sexagenary date cycle was Gui Wei. This date corresponds to November 6th, 1671 in the Gregorian calendar.

Note: According to the calculation of the Datong system, The conjunction associated with the first month (New Year day) was on a Gui Chou day (February 9th, 1671), which was one day earlier than the Jia Yin day (February 10th, 1671) indicated in the calendar. The other conjunction dates in the calendar match the calculation of the Datong system. All the dates and times of solar terms given in the calendar agree with the calculation of the Datong system.

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The last row in the photo is omitted in the following table.

Translation

The following table omits columns 4-6.

According to the calculation of the Datong system, the leap months in the 4th and 7th year of the Yongli reign were after the 11th and 7th month, respectively, and they are inconsistent with this table. Surprisingly, in the calendar for the 30th year of the Yongli reign and the calendar for the 31st year of the Yongli reign, the leap month in the 7th year of the Yongli reign is recorded to be after the 8th month, inconsistent with both this table and the calculation of the Datong system.