Hisashige Tanaka, an engineer at the end of the Edo period, known by the nickname "Karakuri-Giemon （The Gadget Wizard Giemon）" made an historic perpetual chronometer, the so-called "Man-nen dokei" （this literally means a clock that works for tens of thousands of years）, which is the best work in traditional Japanese clocks, in 1851 as the summation of his skills. With the temporal hour system of the Edo period based on sunrise and sunset, both day and night were divided into six equal parts, and each basic unit of time was called a "koku," so that the length of a "koku" differed between day and night, as well as changing from season to season. A conventional old Japanese clock required replacement of the panel depending on the season. However, this Man-nen dokei was epoch-making in that just by winding a spring once a year it could automatically move the pieces showing the clock times corresponding to the season, and it could be used all year round.

 The Man-nen dokei is crowned with a celestial globe that shows the positions of the sun and the moon, and beneath are six multifunctional clock faces: 1） a traditional Japanese clock with Japanese figures to show clock time, 2） a clock plate with 24 seasonal datum points, 3） a display of the seven days of the week and number of sounds to tell the time, 4） a display of dates by sexagenary cycle, 5） a display of the age of the moon, and 6） a Western clock. With energetic challenging spirit, Hisashige Tanaka tried to automatically display for one year, by using a spring mechanism, all the information concerning "time" and "calendars" that the people of Edo period needed by utilizing new knowledge and technology that came from Western countries at the end of the Edo period. The Man-nen dokei not only has originality and the idea of a mechanism where the entire system works in conjunction, but also beautiful decorations of Japan, mother-of-pearl, and metal carving, making it exemplary of the fruits of the skills of an artisan.

 With the Man-nen dokei, pieces to show the time automatically move, coping with the temporal hour system of the Edo period, and change the length of clock time.

 What enabled the realization of this was an insect-shaped gear. The gear is very much different from an ordinary gear, and the angles and intervals of the eight gear teeth are different. To know how the insect-shaped gear operates, a gear that satisfies the target operation of day and night was designed and produced by using knowledge of modern astronomy, and a gear copying the insect-shaped gear of the Man-nen dokei was made, followed by an experiment conducted to compare these. As a result, concerning the operation of the insect-shaped gear, it was verified that the difference from the target operation is small, although there is a small time lag when reversing and the revolution of the gear is smooth.

 It is amazing that the artisan, Hisashige Tanaka, understood advanced astronomy and realized almost every feature of the Man-nen dokei by manual work, and it shows the excellence of his knowledge and skill.

 The Man-nen dokei did not just introduce and use the advanced knowledge and technology of Western countries, but was made to fit in with the lives and culture of the Japanese people. The technology of the Man-nen dokei, which displays the difference in seasons and time in accordance with the natural lapse of time, questions us who live in modern times, in particular, about the desired relationship between spiritual wealthy and science and technology.