The , officially known as the Tenpō sexagenary unitary calendar (天保壬寅元暦 ''Tenpō jin'in genreki''), was a Japanese
lunisolar calendar
A lunisolar calendar is a calendar in many cultures, that combines monthly lunar cycles with the solar year. As with all calendars which divide the year into months, there is an additional requirement that the year have a whole number of mont ...
. It was published in the ''
Tenpō
was a after '' Bunsei'' and before '' Kōka.'' The period spanned from December 1830 through December 1844. The reigning emperor was .
Introduction
Change of era
* December 10, 1830 () : In the 13th year of ''Bunsei'', the new era name of ...
'' era (1830–1844) it remained in use throughout the late
Edo period
The , also known as the , is the period between 1600 or 1603 and 1868 in the history of Japan, when the country was under the rule of the Tokugawa shogunate and some 300 regional ''daimyo'', or feudal lords. Emerging from the chaos of the Sengok ...
, from 1844 to 1872.
[Orchiston, Wayne ''et al.'' (2011)]
''Highlighting the History of Astronomy in the Asia-Pacific Region,'' p. 155
History
The ''Tenpō-reki'' system was developed by . Marking the final traditional calendar system devised by Japanese astronomers and mathematicians.
Overview
The Tenpō calendar is a lunisolar system which adopted
Teiki-hō method, dividing
solar terms
A solar term (or ''jiéqì'', zh, t=節氣, s=节气) is any of twenty-four periods in traditional Chinese lunisolar calendars that matches a particular astronomical event or signifies some natural phenomenon. The points are spaced 15° apart ...
by solar longitude instead of time, unlike the previous
Heiki-hō method. It begins each lunar month on the day of the new moon and adds a
leap month
Intercalation or embolism in timekeeping is the insertion of a leap day, week, or month into some calendar years to make the calendar follow the seasons or moon phases. Lunisolar calendars may require intercalations of days or months.
Solar ca ...
when necessary- specifically when three lunar months occurs between those including a solstice/equinox. the leap month lacks any
''chūki'' 中気 (one of the twelve solar terms that are used to determine the months of the year), and is inserted accordingly. Solstice and equinox consistently fall within the second, fifth, eighth and eleventh months. Observations from
Kyoto
Kyoto ( or ; Japanese language, Japanese: , ''Kyōto'' ), officially , is the capital city of Kyoto Prefecture in the Kansai region of Japan's largest and most populous island of Honshu. , the city had a population of 1.46 million, making it t ...
dictates the time used for determining solar terms and lunar phases.
Unlike previous calendars with uniform hours lengths, the Tenpō calendars hour vary seasonally, posing the length of hours changed depending on the time of year.
[Jessica Kennett Cork. ''The Lunisolar Calendar: A Sociology of Japanese Time''.] This made it extremely challenging to make
Japanese mechanical clocks.
The Tenpō calendar is no longer officially maintained.
Known problems
The Tenpō calendar's assume of fixed month either two or three full lunar months will always occur between such months, containing Solstice and equinoxes. When there are three, that there will be one month without a ''chūki'' to be designated as the leap month. It does not clearly define how to treat the case where there is only one full interceding lunar month, nor when such a period contains more than one month not containing any ''chūki''. In 2033, for the first time in the calendar's history, there will be only one complete lunar month between the autumnal equinox and winter solstice, and two ''chūki''-less months between the winter solstice and 2034 spring equinox. This situation leads to what is called the .
See also
*
Japanese calendar
Japanese calendar types have included a range of official and unofficial systems. At present, Japan uses the Gregorian calendar together with year designations stating the Japanese era name, year of the reign of the current Emperor. The written f ...
*
Sexagenary cycle
The sexagenary cycle, also known as the gānzhī (干支) or stems-and-branches, is a cycle of sixty terms, each corresponding to one year, thus amounting to a total of sixty years every cycle, historically used for recording time in China and t ...
*
Tenpō
was a after '' Bunsei'' and before '' Kōka.'' The period spanned from December 1830 through December 1844. The reigning emperor was .
Introduction
Change of era
* December 10, 1830 () : In the 13th year of ''Bunsei'', the new era name of ...
References
External links
*
National Diet Library
The is the national library of Japan and among the largest libraries in the world. It was established in 1948 for the purpose of assisting members of the in researching matters of public policy. The library is similar in purpose and scope to ...
"The Japanese Calendar"
{{DEFAULTSORT:Tenpo calendar
Specific calendars
History of science and technology in Japan
Time in Japan
1844 establishments in Asia
1872 disestablishments in Asia