The Japanese calendar
An introduction to the traditional lunisolar calendar, along with explanations of its relationship to telling time and identifying directions.
The Five Elements, Ten Stems, and Twelve Branches
The classical Japanese calendar was based on a complex cosmological system imported from China. At the core of this system were the Five Elements (go-gyō) of wood (ki), fire (hi), earth (tsuchi), metal (kin; pronounced "ka" in this system), and water (mizu). Each element was further divided into yang and yin aspects, the former designated by the Chinese character for "elder brother" and pronounced "e," the latter designated by the Chinese character for "younger brother" and pronounced "to." The result was a series of Ten Stems (jikkan). Each stem was given a separate Sinicized name, and these Sinicized readings formed the basis of a style of enumeration that is still used, for instance, in legal contracts and theater seating arrangements. Indeed, most modern Japanese will be able to rattle off the first three or four of these stems with ease, although the others may well cause trouble.
The following table lists the Ten Stems, showing their derivation from the yang and yin aspects of the Five Elements. The relevant Chinese character may be read in either Japanese or Sinicized fashion; the latter is the form used for enumerative purposes:
|Element||Japanese reading||Chinese character||Sinicized reading|
|Wood (yang)||ki-no-e （木の兄）||甲||kō|
|Wood (yin)||ki-no-to （木の弟）||乙||otsu|
|Fire (yang)||hi-no-e （火の兄）||丙||hei|
|Fire (yin)||hi-no-to （火の弟）||丁||tei|
|Earth (yang)||tsuchi-no-e （土の兄）||茂||ho|
|Earth (yin)||tsuchi-no-to （土の弟）||己||ki|
|Metal (yang)||ka-no-e （金の兄）||庚||kō|
|Metal (yin)||ka-no-to （金の弟）||辛||shin|
|Water (yang)||mizu-no-e （水の兄）||壬||jin|
|Water (yin)||mizu-no-to （水の弟）||癸||ki|
The Twelve Branches (jūni-shi) comprise the signs of the traditional Chinese zodiac, which were given the names of animals (the Western zodiac, of course, also contains 12 signs). These signs were used to designate hours of the day and directions (see the other tabs for details). They are also the versions found today on Japanese New Year's cards. The following table lists the signs by their English name, the conventional Chinese character used to represent the sign, the Japanese reading for each character, and the standard Chinese character currently used to represent the same animal (note that in Japan, the Chinese "goat" is treated as "sheep" and "pig" is treated as "boar"):
|Sign||Chinese character||Japanese reading||Standard modern character|
Finally, the Ten Stems and the Twelve Branches were matched sequentially in pairs -- always with one of the Five Elements first, beginning with wood, or ki -- to yield a total of 60 possible combinations. This method of sequential matching provided the system as a whole with its name: the Eto （干支, or "Stem-Branch"）System. This system is most commonly used today to identify the year of a person's birth, so that when an individual has completed the entire cycle of 60 and reached the year with the same sign as that person's year of birth, it is referred to as the person's kanreki (that is, having reached the 61st calendar year of one's life, although now kanreki is usually used simply to refer to one's 60th birthday). The possible permutations are as follows:
|Year no.||Chinese compound||Japanese Eto reading||Sinicized reading|
|甲子||ki-no-e ne [repeated]||kasshi [repeated]|
The phases of the moon (getsurei) and names of the months
The traditional Japanese calendar was a lunisolar calendar, and great attention was paid to the phases of the moon. A lunar month started and ended with the new moon (shingetsu), and a full moon (mochizuki or mangetsu) marked the middle of the month. Special terms were (and still are) used to describe the two half moons, the first appearing on day seven or eight of the month and the second on day 22 or 23: jōgen no tsuki (上弦の月, so called because the appearance of the setting moon was compared to a bow with its drawstring at the top) and kagen no tsuki (下弦の月, the appearance of the setting moon resembling a bow with its drawstring at the bottom).
The following table lists the other names that were used to describe the different phases of moon during the course of the month (hyphens added for clarity):
|Term for the moon||Japanese||Approx. day of lunar month
Approx. time of moonrise
|shingetsu / tsugomori||新月 / つごもり||30th day of the month
|futsuka-zuki||二日月||2nd day of the month
|mika-zuki||三日月||3rd day of the month
|nanoka-zuki||七日月||7th day of the month
|yōka-zuki||八日月||8th day of the month
|kokonoka-zuki||九日月||9th day of the month
|tōka-amari no tsuki||十日余りの月||11th day of the month
|jūsan'ya-zuki / komochi-zuki||十三夜月||13th day of the month
|mochi-zuki / mangetsu||望月 / 満月||15th day of the month
|izayoi-zuki||十六夜月||16th day of the month
|tachimachi-zuki||立ち待ち月||17th day of the month
|imachi-zuki||居待ち月||18th day of the month
|伏し待ち月 / 寝待ち月||19th day of the month
9 p.m. (ariake, or lingering moon, from about this point)
|更け待ち月 / 二十日月||20th day of the month
|hatsuka-amari no tsuki||二十日余りの月||22nd day of the month
|nijūsan'ya-zuki||二十三夜月||23rd day of the month
The names of the months
The months, though often simply called the First Month, the Second Month, and so on, also had a variety of other names. The table below gives the most common traditional names for the 12 lunar months, along with the corresponding season and two common name variants. For the problem of how synchronization with the solar year was handled, see the next tab.
|Mutsuki||睦月||Spring||Hatsutsuki （初月）, Shōgatsu （正月）|
|Kisaragi||如月||Umemizuki （梅見月）, Yukigezuki （雪消月）|
|Yayoi||弥生||Hanamizuki （花見月）, Sakurazuki （桜月）|
|Uzuki||卯月||Summer||Natsuhazuki （夏初月）, Hananokoshizuki （花残月）|
|Satsuki||皐月||Sakumozuki （さくも月）, Tagusazuki （田草月）|
|Minazuki||水無月||Kazemachizuki （風待月）, Seminohazuki （蝉葉月）|
|Fuzuki||文月||Autumn||Akihazuki （秋初月）, Tanabatazuki （七夕月）|
|Hazuki||葉月||Katsurazuki （桂月）, Kosomezuki （木染月）|
|Nagatsuki||長月||Nezamezuki （寝覚月）, Momijizuki （紅葉月）|
|Kannazuki||神無月||Winter||Shigurezuki （時雨月）, Koharu （小春）|
|Shimotsuki||霜月||Yukimizuki （雪見月）, Kamigaerizuki （神帰月）|
|Shiwasu||師走||Umehatsuzuki （梅初月）, Harumachizuki （春待月）|
The 24 solar terms (nijūshi sekki)
Solar terms (sekki -- 節気), which mark points 15 degrees apart along the solar elliptic, were used to signal seasonal events and also to reconcile the differences that arose between the lunar calendar and the solar year. The winter solstice served as the starting point for making these calculations (the winter solstice was by convention assigned to the Eleventh Month). Each month had two points -- a setsu （節） and a chū （中） -- and each point was assigned a name associated with a particular season. The chū points provided the basis for numbering the sequence of the lunar (calendrical) months, thus establishing the connection between the two systems.
Intercalary months (urūzuki -- 閏月) were inserted when the discrepancy between the solar year (the distance between two chū points being about 30.4 days) and the nominally 30-day lunar calendar (in which the moon completes its cycle in about 29.5 days) left a month without a solar chū point, which in classical times happened about once every three years. The extra "empty" month (that is, lacking the chū point necessary for establishing a position in the overall sequence) was given the same number as the previous month, preceded by the term jun （閏）. Thus, jun-nigatsu would be the Intercalary Second Month of the year, following the usual Second Month. The addition of the extra month would bring the two systems back into alignment. Years with the standard 12 lunar months actually contained 354 or 355 days, while years with intercalary months were either 383 or 384 days long. It was a cumbersome system, further complicated in 1844 by the adoption of an alternate method for measuring the distance traveled by the sun throughout different parts of the year (the latter system is what constitutes the kyūreki -- "old calendar" -- as it is understood today).
The following table gives the names of the 24 solar terms, along with approximate equivalents in the Gregorian system (approximate because the precise date depends upon the year):
|Season|| Solar term
|Name||Japanese||Approximate Gregorian equivalent|
|Spring||shōgatsu-setsu||risshun (beginning of the year)||立春||February 4|
|nigatsu-chū||shunbun (spring equinox)||春分||March 21|
|Summer||shigatsu-setsu||rikka (start of summer)||立夏||May 6|
|gogatsu-chū||geshi (summer solstice)||夏至||June 21|
|Autumn||shichigatsu-setsu||risshū (start of autumn)||立秋||August 8|
|hachigatsu-chū||shūbun (autumn equinox)||秋分||September 23|
|Winter||jūgatsu-setsu||rittō (start of winter)||立冬||November 8|
|jūichigatsu-chū||tōji (winter solstice)||冬至||December 22|
Time and directions
In addition to their role as signs of the zodiac, the Twelve Branches were also used to refer to times of the day and geographical directions. The following diagrams illustrate the relationships (the diagrams may be freely reproduced in printed form -- with an appropriate attribution -- but online use is prohibited).
The day was divided into halves, with the two-hour period centered on midnight designated as the Hour of the Rat. When finer distinctions were necessary, the two-hour periods were divided into numbered quarters of 30 minutes each; the designation ushi-mitsu, or "ox-three," for example, would refer to the 30-minute period between 2:00 am and 2:30 am, the third quarter of the Hour of the Ox.
Another way of calculating time seems to have been based on the importance to divination of multiples of nine, so that the first instance (corresponding to midnight) is kokonotsudoki ("nine of the clock") and a countdown of sorts begins from that point, with two times nine equal to 18, which -- ignoring the leading digit -- yields yatsudoki ("eight of the clock"), three times nine equals 27, and hence 27 --> 7 --> nanatsudoki ("seven of the clock"), and so on, down to yotsudoki ("four of the clock"). The points midway to the next "hour" were designated "halfway" points (-han; ~半).
There were variations on this system in different historical periods, other terms exist for different ranges of time within the 24-hour day, and in addition there is a theory that holds that the Hour of the Rat actually began at midnight, so that the method indicated by the diagram cannot be considered perfectly reliable in all cases.
Each of 12 directions took the name of one of the Branches, beginning with "Rat" in the north, and special designations were added for the northeast, southeast, southwest, and northeast based on the names of the two adjoining Branches. The northeast and southwest were considered unlucky directions (kimon and ura-kimon, respectively), forming the basis for the practice of avoiding travel in those directions (katatagae).