Tenpō calendar
The Tenpō calendar, officially the Tenpō sexagenary unitary calendar (天保甲戌元暦 Tenpō jin'in genreki), was the Japanese calendar in use in the late Edo period, from 1844 to 1872.
The calendar was a lunisolar calendar with 355 days in a year. The length of months was either 29 or 30 days and calculated to match the actual lunar cycle. A leap month was added seven times in a nineteen-year cycle. Each month was synchronized with the sexagenary cycle of Ten Celestial Stems and Twelve Branches, the Twenty-Eight Lunar Mansions, the Eight Warrior Deities, the Five Phases, and the Nine Irregular Days, or Zassetsu (雑節). The only Zassetsu still celebrated in Japan today is setsubun.
In previous calendars, hours were of uniform lengths. In the Tenpō calendar, the length of hours changed depending on the time of year.[1] This made it extremely difficult to make Japanese mechanical clocks.
References
- ^ Jessica Kennett Cork. The Lunisolar Calendar: A Sociology of Japanese Time.
