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The Tenpō calendar (天保暦, Tenpō-reki), officially known as the Tenpō sexagenary unitary calendar (天保壬寅元暦 Tenpō jin'in genreki), was a Japanese lunisolar calendar.^[1] It was published in the Tenpō era (1830–1844) it remained in use throughout the late Edo period, from 1844 to 1872.^[2]

History

The Tenpō-reki system was developed by Shibukawa Kagesuke [ja]. Marking the final traditional calendar system devised by Japanese astronomers and mathematicians.^[2]

Overview

The Tenpō calendar is a lunisolar system which adopted Teiki-hō method, dividing solar terms 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 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^[3]^[4] 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.^[5] 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 Year 2033 Problem [ja].

References

^ Nussbaum, Louis-Frédéric. (2005). "Calendar" in Japan Encyclopedia, p. 98.
^ ^a ^b Orchiston, Wayne et al. (2011). Highlighting the History of Astronomy in the Asia-Pacific Region, p. 155.
^ "暦Wiki/太陰太陽暦/定気法の影響 - 国立天文台暦計算室".
^ "暦Wiki/時刻/日本の本初子午線 - 国立天文台暦計算室".
^ Jessica Kennett Cork. The Lunisolar Calendar: A Sociology of Japanese Time.

External links

National Diet Library, "The Japanese Calendar"

[1] Nussbaum, Louis-Frédéric. (2005). "Calendar" in Japan Encyclopedia, p. 98.

[orchiston155-2] Orchiston, Wayne et al. (2011). Highlighting the History of Astronomy in the Asia-Pacific Region, p. 155.

[3] "暦Wiki/太陰太陽暦/定気法の影響 - 国立天文台暦計算室".

[4] "暦Wiki/時刻/日本の本初子午線 - 国立天文台暦計算室".

[5] Jessica Kennett Cork. The Lunisolar Calendar: A Sociology of Japanese Time.

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[2]

[3]

[4]

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@@ Line 1: / Line 1: @@
+{{Short description|Japanese lunisolar calendar}}
-{{nihongo|'''Tenpō calendar'''|天保暦|Tenpō-reki}}, officially the '''Tenpō sexagenary unitary calendar''' (天保甲戌元暦 ''Tenpō jin'in genreki''), was a [[Japan]]ese [[lunisolar calendar]] (''genka reki'').<ref>[[Louis-Frédéric|Nussbaum, Louis-Frédéric]]. (2005). [http://books.google.com/books?id=p2QnPijAEmEC&pg=PA98&dq= "Calendar"] in ''Japan Encyclopedia'', p. 98.</ref> It was published in the ''[[Tenpō]]'' era (1830-1844).<ref name="orchiston155">Orchiston, Wayne ''et al.'' (2011). [http://books.google.com/books?id=vOUWfhBheDIC&pg=PA155&dq= ''Highlighting the History of Astronomy in the Asia-Pacific Region,'' p. 155].</ref>  It was in use in the late [[Edo period]], from 1844 to 1872.{{citation needed|date=January 2013}}
+The {{nihongo|'''Tenpō calendar'''|天保暦|Tenpō-reki}}, officially known as the '''Tenpō sexagenary unitary calendar''' (天保壬寅元暦 ''Tenpō jin'in genreki''), was a Japanese [[lunisolar calendar]].<ref>[[Louis-Frédéric|Nussbaum, Louis-Frédéric]]. (2005). [https://books.google.com/books?id=p2QnPijAEmEC&pg=PA98&dq= "Calendar"] in ''Japan Encyclopedia'', p. 98.</ref> It was published in the ''[[Tenpō]]'' era (1830&ndash;1844) it remained in use throughout the late [[Edo period]], from 1844 to 1872.<ref name="orchiston155">Orchiston, Wayne ''et al.'' (2011). [https://books.google.com/books?id=vOUWfhBheDIC&pg=PA155&dq= ''Highlighting the History of Astronomy in the Asia-Pacific Region,'' p. 155].</ref>
 ==History==
-The  ''Tenpō-reki'' system was the work of [[Shibukawa Kagesuke]].  This was the last traditional calendar system created by Japanese astronomers and mathematicians.<ref name="orchiston155"/>
+The ''Tenpō-reki'' system was developed by {{Interlanguage link multi|Shibukawa Kagesuke|ja|3=渋川景佑}}. Marking the final traditional calendar system devised by Japanese astronomers and mathematicians.<ref name="orchiston155"/>
 ==Overview==
+The Tenpō calendar is a lunisolar system which adopted [[:jp:定気法|Teiki-hō method]], dividing [[solar terms]] by solar longitude instead of time, unlike the previous [[:jp:平気法|Heiki-hō method]]. It begins each lunar month on the day of the new moon and adds A [[leap month]] when necessary- specifically when three lunar months occurs between those including a solstice/equinox.<!-- What is referred to here? --> the leap month lacks any [[:jp:中気|''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]]<ref>{{Cite web|url=http://eco.mtk.nao.ac.jp/koyomi/wiki/C2C0B1A2C2C0CDDBCEF12FC4EAB5A4CBA1A4CEB1C6B6C1.html|title = 暦Wiki/太陰太陽暦/定気法の影響 - 国立天文台暦計算室}}</ref><ref>{{Cite web|url=http://eco.mtk.nao.ac.jp/koyomi/wiki/BBFEB9EF2FC6FCCBDCA4CECBDCBDE9BBD2B8E1C0FE.html|title=暦Wiki/時刻/日本の本初子午線 - 国立天文台暦計算室}}</ref> dictates the time used for determining solar terms and lunar phases.
-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 [[Metonic cycle]]. Each month was synchronized with the [[sexagenary cycle]] of Ten Celestial Stems and Twelve Branches, the [[Twenty-eight mansions|Twenty-Eight Lunar Mansions]], the Eight Warrior Deities, the [[Wu Xing|Five Phases]], and the Nine Irregular Days, or Zassetsu (雑節). The only Zassetsu still celebrated in Japan today is ''[[setsubun]]''.{{citation needed|date=January 2013}}
-In previous calendars, hours were of uniform lengths. In the Tenpō calendar, the length of hours changed depending on the time of year.<ref>Jessica Kennett Cork. ''The Lunisolar Calendar: A Sociology of Japanese Time''.</ref> This made it extremely difficult to make [[Japanese clock|Japanese mechanical clocks]].
+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.<ref>Jessica Kennett Cork. ''The Lunisolar Calendar: A Sociology of Japanese Time''.</ref> This made it extremely challenging to make [[Japanese clock|Japanese mechanical clocks]].
+The Tenpō calendar is no longer officially maintained.
-Unlike the [[Chongzhen calendar]] which will continue to be accurate into the long-term future, the Tenpō calendar does not perfectly synchronize the lunar and solar cycles, and has started to drift backwards over the years. Also, in the years 2033 and 2034 there will be several months when the system breaks down and there is no legally defined month under this calendar.{{citation needed|date=January 2013}}
+==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 {{Interlanguage link multi|Year 2033 Problem|ja|3=旧暦2033年問題}}.
 ==See also==
@@ Line 26: / Line 30: @@
 {{DEFAULTSORT:Tenpo calendar}}
 [[Category:Specific calendars]]
-[[Category:History of Japan]]
+[[Category:History of science and technology in Japan]]
 [[Category:Time in Japan]]