Calendar system in Japan

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This article describes about calendar system in Japan, and how the date was represented in this wiki.

Japanese old style calender before 1873

In Japan, Gregorian Calendar system was adopted from 1st January, 1873. Before the day, lunisolar calendar system has been applied.

leap months

In lunisolar calendar, a month consists 29 or 30 days. The length of month may vary yearly or monthly.

One year contains 12 months usually, but it is much shorter than solar year (365/366 days). To adjust the gap, the leap month was inserted 7 times in 19 years. For example, in 1868 "leap April" was inserted after the "normal" April. So the year 1868 has 13 months.

name of months

In Japan, each month of year does not have individual name, it is simply called "First month", "Second month", etc. This rule also applies currently. In this wiki, the name of month would be described in English form (Jan, Feb, etc.) even for lunisolar calendar date.

calendar date in high ancient Japan

Lunisolar calendar system was imported from China, around 6th or 7th century. Old records edited in 8th century describes about the historical event with specific date for BC 7th century in earliest, historians unveiled that such dates were reverse-calculated using calendar calculating method in that age (8th century). Therefore such dates must be fictional until the later years of Emperor Kimmei's reign (ended 571).

Date in this wiki

As for the date after 1873, all the date would be described with Gregorian calendar, unless with any notification. Before the date, usually two form of date would be described simultaneously, for example:

2 Dec 1872OS / 31 Dec 1872NS

This example shows the date "2 Dec 1872 in lunisolar calendar (Old Style - OS)" corresponds "31 Dec 1872 in Gregorian calendar (New Style - NS)".

Now in progress to expand date expression

As this Wiki is going to cover much wider range of historical event, I will expand date expression to provide more apparent and avoid-misunderstanding way. The suffixes following to date is now to be:

  • JOS - Japanese Old Style. By lunisonar calender system which was adopted in Japan until 1873.
  • JC - Julian Calender. Used before 1582 (Western Catholic Countries), 18th century (Western Protestant Countries), 20th century (Russia and Eastern Countries).
  • GC - Gregorian Calender. Started to use on 1582 in Western Catholic Countries. Adopted in Japan from 1873. Current de facto standard calendar system in the world.
  • LS - Local Style. Other than above.

Without any suffix, the date should be treated as expressed by the Gregorian Calendar.

Sexagenary cycle

Sexagenary cycle is counting system used for day, month (rarely) or year, originally created in ancient China and widely used in far eastern countries. It is expressed by combination of 10 stems and 12 branches, these creates 60 (least common multiple of 10 and 12) numbers in a cycle.

10 stems

10 stems are also created as combinations of 5 elements (wood, fire, earth, metal, water) and "positive and negative". In Japan, "positive and negative" are corresponded to "senior brother" 兄 -no-e and "junior brother" 弟 -no-to.

stems
(Kanji)
pronounce
in
Japanised
Chinese
pronounce
in
Japanese
element positive
/
negative
expression
in the wiki
Koo Ki-no-e wood positive senior wood
Otsu Ki-no-to negative junior wood
Hei Hi-no-e fire positive senior fire
Tei Hi-no-to negative junior fire
Bo Tsuchi-no-e earth positive senior earth
Ki Tsuchi-no-to negative junior earth
Koo Ka-no-e metal positive senior metal
Shin Ka-no-to negative junior metal
Jin Mizu-no-e water positive senior water
Ki Mizu-no-to negative junior water

12 branches

12 branches are expressed by symbol beast, with following sequence:

branches
(Kanji)
pronounce
in
Japanised
Chinese
pronounce
in
Japanese
symbol
beast
Shi Ne Rat
Chu Ushi Ox
In Tora Tiger
Bo U Rabbit
Shin Tatsu Dragon
Shi Mi Snake
Go Uma Horse
Bi Hitsuji Goat
Shin Saru Monkey
Yu Tori Rooster
Jutsu Inu Dog
Gai I Pig

stems and branches

Combination of stems and branches created a cycle of 60 (days or years).

no Kanji Jap'd Chinese Japanese English no Kanji Jap'd Chinese Japanese English no Kanji Jap'd Chinese Japanese English no Kanji Jap'd Chinese Japanese English no Kanji Jap'd Chinese Japanese English
1 甲子 Koo-shi Ki-no-e Ne Rat, senior wood 2 乙丑 Itsu-chu Ki-no-to Ushi Ox, junior wood 3 丙寅 Hei-in Hi-no-e Tora Tiger, senior fire 4 丁卯 Tei-bo Hi-no-to U Rabbit, junior fire 5 戊辰 Bo-shin Tsuchi-no-e Tatsu Dragon, senior earth
6 己巳 Ki-shi Tsuchi-no-to Mi Snake, junior earth 7 庚午 Koo-go Ka-no-e Uma Horse, senior metal 8 辛未 Shin-bi Ka-no-to Hitsuji Goat, junior metal 9 壬申 Jin-shin Mizu-no-e Saru Monkey, senior water 10 癸酉 Ki-yu Mizu-no-to Tori Rooster, junior water
11 甲戌 Ko-jutsu Ki-no-e Inu Dog, senior wood 12 乙亥 Itsu-gai Ki-no-to I Pig, junior wood 13 丙子 Hei-shi Hi-no-e Ne Rat, senior fire 14 丁丑 Tei-chu Hi-no-to Ushi Ox, junior fire 15 戊寅 Bo-in Tsuchi-no-e Tora Tiger, senior earth
16 己卯 Ki-bo Tsuchi-no-to U Rabbit, junior earth 17 庚辰 Koo-shin Ka-no-e Tatsu Dragon, senior metal 18 辛巳 Shin-shi Ka-no-to Mi Snake, junior metal 19 壬午 Jin-go Mizu-no-e Uma Horse, senior water 20 癸未 Ki-bi Mizu-no-to Hitsuji Goat, junior water
21 甲申 Koo-shin Ki-no-e Saru Monkey, senior wood 22 乙酉 Itsu-yu Ki-no-to Tori Rooster, junior wood 23 丙戌 Hei-jutsu Hi-no-e Inu Dog, senior fire 24 丁亥 Tei-gai Hi-no-to I Pig, junior fire 25 戊子 Bo-shi Tsuchi-no-e Ne Rat, senior earth
26 己丑 Ki-chu Tsuchi-no-to Ushi Ox, junior earth 27 庚寅 Koo-in Ka-no-e Tora Tiger, senior metal 28 辛卯 Shin-bo Ka-no-to U Rabbit, junior metal 29 壬辰 Jin-shin Mizu-no-e Tatsu Dragon, senior water 30 癸巳 Ki-shi Mizu-no-to Mi Snake, junior water
31 甲午 Koo-go Ki-no-e Uma Horse, senior wood 32 乙未 Itsu-bi Ki-no-to Hitsuji Goat, junior wood 33 丙申 Hei-shin Hi-no-e Saru Monkey, senior fire 34 丁酉 Tei-yu Hi-no-to Tori Rooster, junior fire 35 戊戌 Bo-jutsu Tsuchi-no-e Inu Dog, senior earth
36 己亥 Ki-gai Tsuchi-no-to I Pig, junior earth 37 庚子 Koo-shi Ka-no-e Ne Rat, senior metal 38 辛丑 Shin-chu Ka-no-to Ushi Ox, junior metal 39 壬寅 Jin-in Mizu-no-e Tora Tiger, senior water 40 癸卯 Ki-bo Mizu-no-to U Rabbit, junior water
41 甲辰 Koo-shin Ki-no-e Tatsu Dragon, senior wood 42 乙巳 Itsu-shi Ki-no-to Mi Snake, junior wood 43 丙午 Hei-go Hi-no-e Uma Horse, senior fire 44 丁未 Tei-bi Hi-no-to Hitsuji Goat, junior fire 45 戊申 Bo-shin Tsuchi-no-e Saru Monkey, senior earth
46 己酉 Ki-yu Tsuchi-no-to Tori Rooster, junior earth 47 庚戌 Koo-jutsu Ka-no-e Inu Dog, senior metal 48 辛亥 Shin-gai Ka-no-to I Pig, junior metal 49 壬子 Jin-shi Mizu-no-e Ne Rat, senior water 50 癸丑 Ki-chu Mizu-no-to Ushi Ox, junior water
51 甲寅 Koo-in Ki-no-e Tora Tiger, senior wood 52 乙卯 Itsu-bo Ki-no-to U Rabbit, junior wood 53 丙辰 Hei-shin Hi-no-e Tatsu Dragon, senior fire 54 丁巳 Tei-shi Hi-no-to Mi Snake, junior fire 55 戊午 Bo-go Tsuchi-no-e Uma Horse, senior earth
56 己未 Ki-bi Tsuchi-no-to Hitsuji Goat, junior earth 57 庚申 Koo-shin Ka-no-e Saru Monkey, senior metal 58 辛酉 Shin-yu Ka-no-to Tori Rooster, junior metal 59 壬戌 Jin-jutsu Mizu-no-e Inu Dog, senior water 60 癸亥 Ki-gai Mizu-no-to I Pig, junior water

transform table

see each year page from Year table page.

Other calendar systems

Lunisolar calendar system in China

Lunisolar calendar system used in premodern Japan, was actually imported from China, supposed in 6th or 7th century. In China, lunisolar calendar system was used until 1911 officially, and still alive unofficially.

Lunisolar calendar methodology between in China and in Japan, were almost same. However, lunisolar system can create timezone difference based on the observation point. For example, think that new moon (Earth - Moon - Sun in column) was observed on 0.30am of a day in Japan (Kyoto), even in China (Beijing), it should be observed same time. But according to the timezone difference, new moon occur on 11.30pm of the previous day in China. It cause lunar month starts in different day between in China and Japan.

Please note that lunisolar calendar date can be different between China and Japan. Even within China, separated administration could cause multiple expression of date.

3 standard of January

There are 3 standard how to put January in the year.

  • Zhou standard 周正. January was put on month of Rat 子, the lunar month includes winter solstice.
  • Yin standard 殷正. January was put on month of Ox 丑, the next (except leap month) of Rat in lunar month (ie. winter solstice is in December).
  • Xia standard 夏正. January was put on month of Tiger 寅, following month of Ox (ie. winter solstice is in November). Usually this is used as de-facto standard.

Islamic calendar

Islamic calendar (IC) system is pure lunar calendar, Islamic year is much shorter than solar year, new year can come in Winter, or in Summer by year. It was rarely used in (both premodern and modern) Japan, but recently become a little more popular.

month of year name length
1st month Muharram 30
2nd month Safar 29
3rd month Rabi al-awwal 30
4th month Rabi al-thani 29
5th month Jumada al-awwal 30
6th month Jumada al-Thani 29
7th month Rajab 30
8th month Shaban 29
9th month Ramadan 30
10th month Shawwal 29
11th month Dhu al-Qadah 30
12th month Dhu al-Hijjah 29 / 30 in leap year

Julian day

  • Julian day (JDN Julian Day Number) is the integer number of continuous days started 1 Jan 4713BC in Julian calendar.
  • Julian date (JD) expresses the time which started 12.00UTC (noon) in the day 1 Jan 4713BC in Julian calendar, by unit day with fraction. JDN for 1 Jan 2017 is 2457755, so the 12.31.19JST (UTC+9H), 1 Jan 2017 will be expressed as:
    • 2457755 + (12-9)/24 + 31/(24*60) + 19/(24*60*60) - 0.5 = 2457754.646747686

reference