Traditional Chinese timekeeping

The traditional Chinese time systems refers to the time standards for divisions of the day used in China until the introduction of the Shixian calendar in 1628 at the beginning of the Qing dynasty.
Han-era system.
The third chapter of the Huainanzi outlines 15 hours during daylight. These are dawn (), morning light (), daybreak (), early meal (), feast meal (), before noon (), noon (), short shadow (), evening (), long shadow (), high setting (), lower setting(), sunset (), twilight (), rest time (). These are correlated to each hour from 06:00 to 20:00 on the 24-hour clock.
East Han to Ming system.
This system used two standards to measure the time in a solar day. Times during daylight were measured in the "Shí-kè" standard, and at night were measured using the "Gēng-diǎn" standard.
During daylight: "Shí-kè".
The "Shí-kè" ( - ) system is derived from the position of the sun.
Dual hour: Shí.
Each "shí" () was of the time between one midnight and the next, making it roughly double the modern hour. These dual hours are named after the earthly branches in order, with midnight in the first "shí". This first "shí" traditionally occurred from 23:00 to 01:00 on the 24-hour clock with midnight in the middle of the first "shí", but was changed during the Song dynasty so that the first "shí" fell from 00:00 to 02:00 with midnight at the beginning of it.
Starting from the end of the Tang Dynasty into the Song Dynasty, each "shí" was divided into two, with the first half of each "shí" called the initial hour () and the second called the central hour (). Using the change of the midnight hour and the first "shí" above, you could say that during the Song Dynasty midnight went from the central hour of the first "shí" () to the initial hour of the first "shí" ().
One-hundredth of a day: Kè.
Days were also divided into smaller units, called "kè" (). One "kè" was usually defined as of a day until 1628, though there were short periods before then where days had 96, 108 or 120 "kè". "Kè" literally means "mark" or "engraving", referring to the marks placed on sundials or water clocks to help keep time.
Using the definition of "kè" as of a day, each "kè" is equal to 0.24 hours, 14.4 minutes, or 14 minutes 24 seconds. Every "shí" will contain 8 "kè", with 7 or 8 full "kè" and partial beginning and/or ending "kè". These fractional "kè" are multiples of "kè", or 2 minutes 24 seconds. The 7 or 8 full "kè" within each "shí" were referred to as "major "kè"" (). Each of a "kè" was called a "minor "kè"" ().
Describing the time during daylight.
Both "shí" and "kè" would be used to describe the time accurately. There are two ways of doing this.
Smaller time units.
Fēn.
"Kè" were subdivided into smaller units, called "fēn" (). The number of "fēn" in each "kè" varied over the centuries, but a "fēn" was generally defined as of a day. Using this definition, one "fēn" is equal to 14.4 seconds. This also means that a "fēn" is of a major "kè" and of a minor "kè".
Miǎo.
In 1280, Guo Shoujing's Shòushí Calendar () had each "fēn" subdivided into 100 "miǎo" (). Using the definition of "fēn" as 14.4 seconds, each "miǎo" was 144 milliseconds long.
Shùn and niàn.
Each "fen" was subdivided into "shùn" (), and "shùn" were subdivided into "niàn" ().
The Mahāsāṃghika, translated into Chinese as the "Móhēsēngzhī Lǜ" (Taishō Tripiṭaka 1425) describes several units of time, including "shùn" or "shùnqǐng" () and "niàn". According to this text, "niàn" is the smallest unit of time at 18 milliseconds and a "shùn" is 360 milliseconds. It also describes larger units of time, including a "tánzhǐ" () which is 7.2 seconds long, a "luóyù" () which is 2 minutes 24 seconds long, and a "xūyú" (), which is of a day at 48 minutes long.
During night: "Gēng-diǎn" system.
The "Gēng-diǎn" ( - ) system uses predetermined signals to define the time during the night.
One-tenth of a day: "Gēng".
"Gēng" () is a time signal given by drum or gong. The drum was sounded by the drum tower in city centers, and by night watchman hitting a gong in other areas. The character for "gēng" , literally meaning "rotation" or "watch", comes from the rotation of watchmen sounding these signals.
The first "gēng" theoretically comes at sundown, but was standardized to fall at codice_24, or 19:12. The time between each "gēng" is of a day, making a "gēng" 2.4 hours—or 2 hours 24 minutes—long.
The 5 "gēngs" in the night are numbered from one to five: "yī gēng" () (alternately "chū gēng" () for "initial watch"); "èr gēng" (); "sān gēng" (); "sì gēng" (); and "wǔ gēng" (). The 5 gēngs in daytime are named after times of day listed in the Book of Sui, which describes the legendary Yellow Emperor dividing the day and night into ten equal parts. They are morning (); midmorning, (); noon, (); afternoon (); and evening ().
As a 10-part system, the "gēng" are strongly associated with the 10 celestial stems, especially since the stems are used to count off the "gēng" during the night in Chinese literature.
One-sixtieth of a day: "Diǎn".
"Diǎn" (), or point, marked when the bell time signal was rung. The time signal was released by the drum tower or local temples.
Each "diǎn" or point is of a day, making them 0.4 hours, or 24 minutes, long. Every sixth "diǎn" falls on the "gēng", with the rest evenly dividing every "gēng" into 6 equal parts.
Describing the time during the night.
Gēng and diǎn were used together to precisely describe the time at night.
The night length is inconsistent during a year. The nineteenth volume of the Book of Sui says that at the winter solstice, a day was measured to be 60% night, and at the summer solstice, only 40% night. The official start of night thus had a variation from 0 to 1 "gēng".
This variation was handled in different ways. From the start of the Western Han dynasty in 206 BC until 102 AD, "yīgēng" was moved back one "kè" every 9th day from the winter solstice to the summer solstice, and moved forward one "kè" every 9th day from summer solstice to the winter solstice. The Xia Calendar (), introduced in 102 AD, added or subtracted a "kè" to the start of night whenever the sun moved 2.5° north or south from its previous position.
Modern applications.
Chinese still uses characters from these systems to describe time, even though China has changed to the UTC standards of hours, minutes, and seconds.
"Shí" is still used to describe the hour. Because of the potential for confusion, "xiǎoshí" (, literally "small hour") is sometimes used for the hour as part of a 24-hour cycle, and "shíchen" () is used for the hour as part of the old 12-hour cycle.
"Diǎn" is also used interchangeably with "shí" for the hour. It can also be used to talk about the time on the hour—for example, 8 o' clock is written as 8 "diǎn" ().
"Fēn" is also used for minutes. To avoid confusion, sometimes the word "fēnzhōng" (, literally "clock minute") is used to clarify that one is talking about modern minutes. The time 09:45 can thus be written as "9 "shí", 45 "fēn"" () or "9 "diǎn", 45 "fēn"" ().
"Kè" has been defined as of a day since 1628, so the modern "kè" equals 15 minutes and each double hour contains exactly 8 "kè". Since then, "kè" has been used as shorthand to talk about time in of a double hour or of a single hour. Their usage is similar to using "quarter hour" for 15 minutes or "half an hour" for 30 minutes in English. For example, 6:45 can be written as "6 "diǎn", 3 "kè"" ().
"Miǎo" is now the standard term for a second. Like "fēn", it is sometimes written as "miǎozhōng" (, literally "clock second") to clarify that someone is talking about modern seconds.