Japanese calendar
Introduction
In 604 Japan adopted the Chinese calendar, [1] This calendar, or a modification of it, was used by Japan until 1873, when it adopted the Gregorian (modern Western) calendar as the official calendar. [2] However, as almost all source materials for events in Japan before 1873 use the Japanese calendar, as do Japanese historians, this Wiki uses the Japanese calendar in principle. (See Dates.)
Dates in Japanese are given as, for example, 10th month, 18th day (十月十八日). Though months do have names, in fact several names (though they are hardly ever used now), numbers are the principle month designations.
The Japanese calendar was "behind" the Western calendar by three to seven and a half weeks, depending on the year, so if one just wants to get a feel for the season based on the Japanese date, it is probably adequate to think of a date one month later. For example, an event of 7/15 happened on Aug. 15, give or take a few weeks (i.e. from the beginning of August to early September). However, to construct a chronology, more must be known.
Characteristics of the Chinese calendar
The Chinese calendar, at least by the time it was adopted in Japan, was not an observational one ("There, we can see the new moon, so the month has started."), but a predictive one, based on calculations, as was necessary for a widely-spread out, developed beaurocracy. The calculation methods were revised at various times, both in China and Japan, so not everything below applies to all periods, especially the way of determining intercalary months.
The Chinese calendar is a lunar, actually a luni-solar, calendar. The start of the month is determined by the new moon, but the position of the month in the year is determined by the solar year, that is, course of the seasons. One should note that although in the the West seasons are considered to begin on the equinoxes and solistices, in the Chinese calendar, the start of spring (立春) is exactly half-way between the winter solistice and the spring equinox, and similarly for other seasons.
Among the characteristics of the Chinese-type calender are the following: [3]
Months start on the day of the new moon.
Months are either 29 or 30 days long. Normally, but not always, 29-day and 30-day months alternate. This means that the date 2/30 is possible, whereas 3/31 is not. Unlike many other calendars, it is [bold] not the case that a particular month is normally a particular length. There is no way of knowing whether a month is 29 or 30 days long except by looking at the calendar for a particular year.
The first month (New Year) starts on the new moon nearest to the first day of spring, Feb. 4 (see above on the starts of seasons). Thus the first month starts between Jan. 20 and Feb. 20. Cite error: Closing </ref> missing for <ref> tag The months are numbered according to the solar point that occurs during that month. For example, the month in which the winter solistice occurs is the 11th month, and the one in which the spring equinox occurs is the 2nd month.
Because the lunar month is less than 1/12 of a solar month. sometimes a month falls entirely between the solar points (中気). In such cases the month is called an intercalary (閏 urru) month, and is given the same number as the previous month. For more, see below on [Bold] Intercalary Months.
Note that sometimes other rules took precendence over those above. It should also be noted that as the calendar was predictive, over time it got removed from astronomical realitiy. For example, by the end of the 16th century the new year started between Jan. 24 and Feb. 24.
Intercalary Months
As the solar year is about 365.25 days but 12 lunar months last only about 354, each year the months start about 11 days earlier with respect to the solar calendar (the seasons) as they did the previous year. In fact, in about two years and eight months, the calendar moves a full month ahead. In order to keep the lunar and solar calendar from getting too far apart, as noted in the characteristics above, when the month gets a full month ahead, the month is given the same number as the preceeding month, but is called an "閏 (uruu)" month. For example, if there are two "third months," the first is called just "third month," but the next is called the "uruu third month". In this Wiki it is refered to as "int. 3", for "intercalary 3rd month". Thus, 1599/3 was followed by 1599/int. 3, which was followed by 1599/4. This type of intercalary month, which can happen any month in the year, is a feature of the Chinese-type luni-solar calendar.
Would it not have been easier just to have thirteen months sometimes instead of sometimes having two 5th months, for example? This is how the luni-solar ancient Babylonian and Jewish calendars work. However, the Chinese calendar keeps months near where they should be. For example, In 1583 there was an int. 1st month. That meant that the second month started on March 24 instead of Feb. 23. March 24th is within the normal starting period for the the 2nd month during that time, but Feb. 23 would have been early for the 2nd month. The 12th month started Jan. 13, 1584, also within the normal time frame for the 12th month. But if there had been no intercalary month, all the months of the year after the first would have started too early, and the 12th month would have started Dec. 14, though months that started from about Nov. 26 to Dec. 23 were supposed to be the 11th month. Thus, the Chinese calendar method keeps the months tightly connected to the solar year and prevents overlaps in the periods in which months can begin.
Calculation Website
Unlike conversions between era years and Western years, which is a fairly easy calculation (see Year dates and Japanese eras, conversion between the Western and Chinese calendar can only be done using a monthly table based on historical documents. One table is Tuchihashi's. However, now there are several websites that provide calcuators which llook up dates. One is the following: http://www.uni-tuebingen.de/geschichte-japans/nengo_calc.htm which will give the Western year for the Japanese date.
Here are several notes on its use:
- "Tsuchihashi" and "Zölner" are the authors of two calendrical tables. For most years they are identical, but in some cases, especially for early years, they are not. To see the problem years use the "" button and use the link given there.
- To use the calculator you have to know the nengô of the year. An explanation of how to do this is found in Japanese eras and the Year dates pages. Or, even easier, run down the list of nengô in the pull-down menu on the calculator until you find the period your year is in. The year in the nengo system is [Wester year] - [Nengo start year] + 1. For example, 1600 is in the Keichô period, which started in 1596. 1600 - 1596 + 1 = 5, so 1600 is Keichô 5. Unfortunately all numbers are in kanji, but you can easily learn the kanji or just count down on the pull-down menu. Note that the intercalary months are preceded by 潤.
- Before entering the month and day, the Western date shown is that of New Year Day of the Japanese year.
- For dates Tenshô 10/9/18 (Oct. 4, 1582) and before, dates are in the Julian calendar, but from the next day, Tenshô 10/9/19 (Oct. 15, 1582) the dates are the Gregorian calendar.
- From 1873 on, the Japanese dates are the Gregorian calendar.
- As this is a European site, the Western dates are given in the order D-M-Y, so 2.6.1465 is June 2, 1465, not February 6.
- There is no calculator on that site for getting from Western to Japanese. So the best way is to pick a Japanese month one month before (like 9 for an October date) and then use the "try and then adjust" method several times.
Notes
- ↑ E. Reishauer, et. al., East Asia: The Great Tradition (Boston: Houghton Mifflin, 1958), p. 476. Before that it appears that some kind of lunar calendar generally following the Chinese seasons was used, as can be seen from dates of the Nihon-gi (Nihon Shoki)(pp. 37-44 of Sources of Japanese Tradition). However, apparently it did not use the Chinese calculations.
- ↑ A standard Japanese lunar calender is still published and can be found in almanac-calendars and daily newspapers. However, it is ignored by most people. It is similar, but not identical to the modern Chinese lunar calendar.
- ↑ Dates below are given in the modern calendar. Also, as Japan is 9 hours east of Greenwich, some years the seasonal date is one day later than that given below.