The Chinese Calendar

The Chinese calendar is a lunisolar calendar. The new moon signaled the first of the lunar month. Their solar year had 12 months each containing either 30 or 31 days. A thirteenth month was added every 2 or 3 years to account for the difference between the year and synodic months.^{[1, p.24]}

The names of the months:^{[1, pp.24-25]}
2 – Xingyue (Apricot Month)
6 – Heyue (Lotus Flower Month)
7 – Qiaoyue
10 – Yangyue (Yang Month)
11 – Dongyue (Winter Month)
12 – Layue (Preserved Foods Month)

“A detailed description on the units of time used in China can be found in official Chinese chronicles (the 24 Chronicles). On the other hand, Japanese units of time did not appear in official histories, like Nihongi, but were scattered in various private histories, diaries, temple records, and so on.”
Soma, et al. (2004)^{[2, p.887]}

Each day had 12 double hours. The day began either at 23 hours local time (most popular) or 0 hours local time (Song Dynasty). In addition to the 12 double hours, each day was equally split into 100 units known as ke. Ke were split into even smaller units known as fen. From, dynasty to dynasty, the amount of fen in a ke varied. Ke and fen were used in Japan but both units there had variations throughout history. Besides a few briefs periods where the number of ke in day was 96, 108, or 120, the “ke = 100 sections of the day” system was used from legendary times until 1628 CE when the number of ke in a day officially became 96.^{[2, p.887]}

The weeks of the Chinese calendar were either 10- or 7-day weeks. The ^{[1, p.25]}

The Chinese have 12 signs in their zodiacs. Although the number is the same as the Greco-Babylonian tradition, the two sets were supposedly developed independently of each other.^{[1, p.24]}

“…the backbone of the Chinese official calendar has remained identical to itself over time…”
Martzloff (2011)^{[3, p.xxxii]}

Units of Time

A Day: 12 double hours. A day was also split into ke but the number of ke in a day can vary depending on the source. The variations are 96, 100, 108, and 120 ke in a day.^{[2, p.887]}

Dian (Tien) (Point): The division of the geng into 5 parts.^{[2, p.888]}

Geng (Keng) (Night Watches): The division of the night into 5 parts.^{[2, p.888]}

Fen: The subdivision of a ke.^{[2, p.887]} In the books of Houhanshu through Songshu, 10 fen = 1 ke. However, in Chapter 19 of Suishu one ke equaled either 60 or 100 fen (the number was dependent of which of the two systems was being used).^{[2, p.893]}

Jie 節: A day where the solar ecliptic longitude is an integral multiple of 30^◦.^{[2, p.888]}

Ke: The subdivisions of a day.^{[2, p.887]}

Mori 没日: The intercalary day added every 70 days or so in order to make the solar ecliptic longitude an integral multiple of 15^◦ on the first day of qi.^{[2, p.888]}

Qi: 1/24 of a year. Each year had 24 qis. This began around 600 BCE. There are two known methods that were used for determining the dates of the qis. The earliest one is known as pingqi 平気 (or hengqi 恒気) and was devised around 550 CE. The latest one is known as dingqi 定気 and was devised in the Qing (Ch’ing) 清 dynasty (1616–1912).^{[2, p.888]}

Zhong 中: A day where the solar ecliptic longitude is an integral multiple of 30^◦.^{[2, p.888]}

History of Chinese Timekeeping

After c.600 BCE: The Chinese started tracking time through a unit they called “qi”.^{[1, p.25]} A qi divided the year starting in the winter solstice into 24 parts consisting of 15 days each. This made the year 360 days long.^{[2, p.888]}

82 CE: The earliest known uses of the word “ke” appeared in Chapters 11, 26, and 75 of Hanshu (edited by Ban Gu). Chapter 26 mentions that ke was altered from 100 units to 120 units for a temporary amount of time.^{[2, p.889]}

432 CE: Fan Ye compiled Houhanshu which contains the earliest known meticulous description of Chinese units of time.^{[2, p.889]}

c.550 CE: Zhang Zixin (張子信) commented that the speed of the sun across the sky fluctuated as the year passed.^{[1, p.25], [2, p.888]}

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References:

[1] – Mondschein, Ken, and Neal Stephenson. On Time: a History of Western Timekeeping. Johns Hopkins University Press, 2020.

[2] – Mitsuru Soma, Kin-aki Kawabata, and Tanikawa Kiyotaka. “Units of Time in Ancient China and Japan,” Publications of the Astronomical Society in Japan 56, no. 5 (October 25, 2004). https://academic.oup.com/pasj/article/56/5/887/2948928. Accessed 6 Jan. 2021.

[3] – Martzloff, Jean-Claude. Astronomy and Calendars – The Other Chinese Mathematics: 104 BC – AD 1644 (2011). Accessed 8 Jan. 2021.

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