Traditional Chinese timekeeping 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

Dating from the Han dynasty, 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 correspond to each hour from 06:00 to 20:00 on the 24-hour clock.

Eastern Han to Ming system

The system used between the Eastern Han and Ming dynasties comprised 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 1/undefined 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, but was changed during the Song dynasty so that it fell from 00:00 to 02:00, with midnight at the beginning. Starting from the end of the Tang dynasty into the Song dynasty, each shí was divided in half, with the first half called the initial hour and the second called the central hour. The change of the midnight hour in the Song dynasty could thus be stated as going 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 1/undefined 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 1/undefined of a day, each kè is equal to 0.24 hours, 14.4 minutes, or 14 minutes 24 seconds. Every shí contains 81/undefined kè, with 7 or 8 full kè and partial beginning or ending kè. These fractional kè are multiples of 1/undefined kè, or 2 minutes 24 seconds. The 7 or 8 full kè within each shí were referred to as "major kè". Each 1/undefined of a kè was called a "minor kè".

Describing the time during daylight

Both shí and kè were used to describe the time, through one of two ways:

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 1/undefined of a day. Using this definition, one fēn is equal to 14.4 seconds. This also means that a fēn is 1/undefined of a major kè and 1/undefined of a minor kè.

Miǎo

In 1280, Guo Shoujing's Shòushí Calendar subdivided each fēn 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 1/undefined 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 yǒu shí central 1 kè, or 19:12. The time between each gēng is 1/undefined 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: yì 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 1/undefined 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, yìgēng 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.

Traditional units in context

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 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 1/undefined 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 1/undefined of a double hour or 1/undefined 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 to clarify that someone is talking about modern seconds.