Man-nen Jimeisho

The perpetual clock, officially ‘Man-nen Jimeisho’ (mechanical stand clock), is a mechanical Japanese-style clock (telling time in temporal hours) that was designed and manufactured by Hisashige Tanaka, also known as ‘Karakuri (gimmick) Giemon’, the founder of Toshiba Corporation, in 1851. One ‘Koku’ is determined by respectively dividing day and night time into six based on dawn and dusk. The clock can not only vary the length of one Koku according to seasons, but also can be automatically activated by winding the spiral spring once a year, while associating the time-indication piece with the season. The clock has a celestial globe on the top part, and six time-indicating areas on the lower part, including the piece-split type Japanese style clock, an entry panel of 24 seasonal turning points, an indication panel for Shichiyo (seven days of the week) and the number of time strikes, a date indication panel according to Jikkan (The Ten Stems) and Junishi (the Twelve Signs of the Chinese Zodiac), a lunar age indication panel and a Western clock. The clock can be said to be the fruit of artisanship, comprising not only the originality of the mechanism, but also the beautiful decorations such as the lacquer work, mother-of-pearl inlay and metal carving.

On exhibition

National Museum of Nature and Science

Hours open:
9:00–17:00 (Entry closes at 16:30.), 9:00–20:00 on Fridays * May be extended for special exhibitions.
Admission fee:
600 yen for general guests/college students, free for high schoolers or younger
Days closed:
Mondays (Tuesday if Sunday or Monday falls on holidays), year-end/New Year’s holidays (Dec. 28–Jan. 1)
7-20 Ueno Koen, Taito-ku, Tokyo 110-8718
URL: access/
5 mins. on foot from JR Ueno Sta. park exit
10 mins. on foot from Ueno Sta., Ginza Line/Hibiya Line
5 mins. on foot from Keisei Ueno Sta., Keisei Line

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