The , officially 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, combining lunar calendars and solar calendars. The date of Lunisolar calendars therefore indicates both the Moon phase and the time of the solar year, that is the position of the Sun in the ...
. 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) and was in use during the late
Edo period
The or is the period between 1603 and 1867 in the history of Japan, when Japan was under the rule of the Tokugawa shogunate and the country's 300 regional '' daimyo''. Emerging from the chaos of the Sengoku period, the Edo period was characte ...
, 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 the work of . This was the last traditional calendar system created by Japanese astronomers and mathematicians.
Overview
The calendar is a lunisolar calendar which adopted
Teiki-hō, where
solar terms
A solar term 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 along the ecliptic and are used by lunisola ...
are equally divided by solar longitude, in place of
Heiki-hō, in which they are equally divided by time. The lunar month starts on a day with a new moon. A
leap month
Intercalation or embolism in timekeeping is the insertion of a leap day, Leap week calendar, week, or month into some calendar years to make the calendar follow the seasons or moon phases. Lunisolar calendars may require intercalations of both d ...
is added when there are three lunar months between a lunar month which includes a solstice/equinox and the following lunar month which includes a solstice/equinox. In that case the leap month is the lunar month which does not include any
''chūki'' 中気 (one of the twelve solar terms that are used to determine the months of the year). The months which include a solstice/equinox are fixed as the second, fifth, eighth and eleventh months respectively. The time of the day used in the calendar to determine the dates of solar terms and lunar phases is that observed at
Kyoto
Kyoto (; Japanese language, Japanese: , ''Kyōto'' ), officially , is the capital city of Kyoto Prefecture in Japan. Located in the Kansai region on the island of Honshu, Kyoto forms a part of the Keihanshin, Keihanshin metropolitan area along wi ...
.
In previous calendars, hours were of uniform lengths. In the Tenpō calendar, 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 calendar's assignment of fixed month numbers on lunar months containing solstices/equinoxes assume that either two or three full lunar months will always occur between such months, and 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 year of the reign of the current Emperor. The written form starts with t ...
*
Sexagenary cycle
The sexagenary cycle, also known as the Stems-and-Branches or ganzhi ( zh, 干支, gānzhī), is a cycle of sixty terms, each corresponding to one year, thus a total of sixty years for one 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 Japanese Calendar"
{{DEFAULTSORT:Tenpo calendar
Specific calendars
History of science and technology in Japan
Time in Japan