Japanese clock

[1] The Nihon Shoki states that Emperor Tenchi made a water clock, or rōkoku (漏刻, literally "leaking" + "cutting, measuring"), in 660 and 671.

Francis Xavier, a Spanish Society of Jesus saint and missionary, gave Ouchi Yoshitaka, a daimyō of the Sengoku period, a mechanical clock in 1551.

[2] The oldest surviving western clock in Japan dates back to 1612; it was given to Shōgun Ieyasu by the viceroy of Mexico (then New Spain).

[3] The Edo period (1603–1868) saw the adaptation of Western techniques to form a unique method of clock making in Japan.

[4] These clocks, called wadokei, were built with different methods in order to follow the temporal hour system (futei jiho 不定時法).

[7] The weights in the nichō-tempu tokei were automatically set for the correct time of day or night with the use of two governors or balances, called tenpu (天府).

[7] The volume on clockmaking contained highly detailed instructions for the production of a weight-driven, striking clock with a verge escapement controlled by a foliot.

[8] Relatively high literacy rates and an enthusiastic, book-lending society contributed greatly to the work's widespread readership.

As such, Japanese timekeepers varied with the seasons; the daylight hours were longer in summer and shorter in winter, with the opposite at night.

Spring driven Japanese clocks were made for portability; the smallest were the size of large watches, and carried by their owners in inrō pouches.

To make a striking clock that told Japanese time, clockmakers used a system that ran two balances, one slow and one fast.

These arms are connected to a single cam with a groove cut in it tuned to the latitude of each watch's individual buyer.

In 1873 the Japanese government adopted Western style timekeeping practices, including equal hours that do not vary with the seasons, and the Gregorian calendar.

Two separate foliot balances allow this 18th-century Japanese clock to run at two different speeds to indicate unequal hours.
Tanaka Hisashige's man-nen dokei ( 万年時計 ) . Completed in 1851.
Drawing of the mechanism of a Japanese clock. Karakuri Zui , 1796.
Tanaka Hisashige 's 1851 myriad year clock displays Japanese, equal hour, and calendar information.
The traditional Chinese 12 Earthly Branches and 24 Cardinal Directions ; the 12 Earthly Branches are the basis for the zodiacal assignments of the Japanese hours.
European lantern clocks such as this one were the starting point for the design of Japanese clocks.