Title

※旧暦 is the colloquial way of referring to the lunisolar calendar, and the antonym of this, 新暦, refers to the use of the solar calendar. 

Era Names of the Nara Period　奈良時代の元号 

Era Names of the Heian Period　平安時代の元号

※In Year 4 of the Jishō Era ( 治承), Emperor Antoku ascended the thrown and the next year's era was changed to the Yōwa Era (養和).  However, this was not recognized by the shogunate in the Kantō Region (関東地方) formed by Minamoto no Yoritomo 源頼朝, where the era name 治承 remained in use. Although the next era Juei (寿永) was recognized in 1183 AD, 治承 was still recognized into the Genryaku Era (元暦) by the Heike Family which harbored the now former Emperor Antoku until their demise in Year 2 of the Genryaku Era (1185 AD).   

Era Names of the Kamakura Period　鎌倉時代の元号

※The end of the Kamakura Period (鎌倉時代) resulted in the bifurcation of the imperial lineage into two factions: the Daikakuji Line (大覚寺統)--the Southern Court (南朝)--and the Jimyōin Line (持明院統)--the Northern Court (北朝). The former was formed by Emperor Kameyama (亀山天皇) and his descendants, whereas the latter started with Emperor Go-Fukakusa (後深草天皇) and exists to the present day. The back and forth between the two courts had gone on for a few decades before both bolstered their respective claimant to the Chrysanthemum Throne. It's at that point in which the Muromachi Period (室町時代)--the Northern-Southern Court Period (南北朝時代)--begins and where there were competing era names. 

※In 1331 AD, Emperor Go-Daigo (後醍醐天皇) changed the era to Genkō (元弘), but this was not recognized by the Kamakura Shogunate as the Shogunate recognized the Southern Court Emperor Kōgon (光厳天皇). 

※In 1332 AD, Emperor Kōgon changed the era name to Shōkei (正慶) as Emperor Go-Daigo was sent into exile, but upon Emperor Go-Daigo's return to the capital, he ruled the name 正慶 invalid and concluded the 'proper' era of 元弘 he had instituted and reformed it to the Kenmu Era (建武). 

Era Names of the Muromachi/Northern-Southern Courts Period 室町時代・南北朝時代の元号

※The administration of Emperor Go-Daigo in the Kenmu Era only lasted for two years before its collapse. The Southern Court recognized this era up until 1336 AD, but the Northern Court recognized it up until 1338 AD. The Sourthern Court's unique eras begin at this point with the Engen Era (1336~1340) whereas for the Northern Court's unique eras, the Kenmu Era is followed by the Ryakuō Era (1338-1342). 

※The Muromachi Period did not end with the reunification of the Northern and Southern Courts. With that, below are the remaining era names that were utilized until the next period of Japanese history.

Era Names of the Sengoku Period　戦国時代の元号

Era Names of the Azuchi-Momoyama Period　安土桃山時代の元号

Era Names of the Edo Period　江戸時代の元号

Era Names Since the Meiji Period　明治時代以降の元号

※The Meiji Period is itself an era name, but it is at the time that each era name has corresponded to a single emperor's reign. The following era names are all familiar and understood by Japanese speakers today. 

Retroactive 年号

Depending on one's interpretation of the starting point of the 'Japanese calendar' is, the true start year is 660 BC when Emperor Jinmu ascended to the thrown. Thus, this year would be 神武（天皇）元年. These retroactive eras are in line with how era names are created today by corresponding to the reign of the emperor of that generation. The difference is that because the 'era name' tradition had not been created until 645 AD, these eras are still colloquially referred to by the emperors' names themselves. These eras are as follows. 

※年号 is more accurate than 元号 in these situations because they technically aren't 'era names' by tradition. Additionally, as for the chart below, the readings of the 年号 will only cover the emperor name in question as 天皇 is read as てんのう in all of them. Colloquially, 天皇 is dropped when stating a date with this method, but it remains in parentheses as its inclusion is more proper.  

※As touched on earlier, 時代 has been used in reference to all eras in modern times beginning with the 明治時代. However, as can be demonstrated from these charts, most other eras did not last very long, some not even lasting a year. In that event, it is customary to use both the traditional date in conjunction with its Western date equivalent. For example, 文明2年（1470年）. If you wanted to refer the general period of time, you would indicate that the period was during the 戦国時代. 

※Having learned so much about the 和暦, it must be noted that how months and days are interpreted must be determined by what time period something was written in. Once Japan switched over to the Gregorian calendar, Japanese society also switched away from various versions of the lunisolar calendar. So, a "January" or "1st month of the year" date written by someone prior to this switch would be referencing the lunisolar year's 1st month and not the Western "January." If a modern writer wishes to reference the old lunisolar months, there are still unique words for those instead of using 1月, 2月, 3月, etc., which could be ambiguous in such a context. Continue reading until the end for coverage on the Japanese lunisolar calendar. 

The next two calendar systems that we will be looking at are of the same nature as the Gregorian calendar. Meaning, their starting points are set at different points in time but their progression remains the same.

1. Its full name being the 神武天皇即位紀元, also known simply as 皇紀,  this calendar starts with the first year of the reign of the first emperor of Japan, Emperor Jinmu. This event is said to have occurred in 660 BC, although whether this is truly historically accurate is up to question as it is based on evidence found in the 日本書紀. This calendar was used prolifically from 1890-1947 AD. Currently, this calendar is only used in Shinto contexts. 
2.  Known as the 天孫紀元, the start date for this calendar is set to when the grandson of the goddess Amaterasu 天照, whose name is Ninigi-no-mikoto 邇邇芸命（ににぎのみこと）, descended to Japan. Although it hasn't ever been widely used, it sets time back essentially 1.8 million years ago, a date so specific it hardly seems like mythology at first.

Known as 干支（かんし・えと） in Japanese, the sexagenary cycle is a system of sixty-year cycles. The system is also marginally extended to months and days. This calendar system has been incredibly influential in Japan as well as many other Asian countries. The system is not only employed to cover years but also months, days, hours, direction, etc. The system is also deeply tied into the 陰陽五行説 (The Theory of Yin-Yang and the Five Elements) with the components being assigned both yin-yang and elemental properties to tie into fortune telling. 

It is thought that it was brought to Japan through the Kofun Period (古墳時代) and the Asuka Period (飛鳥時代). This revolutionary concept of a 'calendar' to Japanese society is believed to have occurred around the year 604 AD (推古12年). 

Each term in the sexagenary cycle is composed of two Kanji, the first being one of the 10 Stems (十干・じっかん) and the second being one of the 12 Branches (十二支・じゅうにし). In Chinese, each stem and each branch has its own respective name, but in Japanese, the naming convention is slightly more complicated.

Firstly, the term えと to refer to the sexagenary cycle as a whole is technically inaccurate as the え and the と respectively derive from the Japanese native wording for the yin-yang breakdown of the names of the Stems as can be seen in the chart below. Yet, what is even more odd is that some speakers mistake えと as referring to the Branches rather than the Stems; however, this understanding is incorrect. 

※The sexagenary calendar is, first and foremost, a Chinese system. Although it has been integrated into Japanese society, the timing of the months and when the new year begins follows the Chinese lunisolar calendar. Knowing the differences between the Chinese and Japanese lunisolar calendar is beyond mental math, but the differences are negligible to begin with. So, the start of Month 1 of this cycle still matches the 

The Ten Stems　十干

Individual stems are called 天干 (Heavenly Stems). Although their primary function is to mark the start of their respective period in the sexagenary cycle, there is a wealth of corresponding information associated with each sign. Aside from yin-yang association, each sign also has a corresponding element, celestial body, and direction.

※Whereas the Chinese readings are truly proper nouns in nature, the Japanese naming convention takes into consideration the elemental and yin-yang properties of the stem calendar sign. In parentheses you will find the literal meaning of the native names of these signs. You'll also notice that the five non-Earth celestial bodies of the Solar System visible to the naked eye (五星) and that "central position" was a part of the traditional five directions (五方) in Chinese society. 

※Aside from being used in the sexagenary calendar, the 10 stems are frequently used in Japan when ranking things similarly to how the Western world uses A, B, C, etc. Because there are 10 stems, this can be used from A-J in the exact order listed above. 

The Twelve Branches　十二支

Individual branches are referred to as 地支 (Earthly Branches). Just like with the Heavenly Stems, the Earthly Branches indicate a lot of information. The system was built by Chinese astronomers who calculated that the orbit of 歳星, the old Chinese word for Jupiter, was approximately 12 years. 

This was then correlated to also identify the 12 months of the year in the lunar calendar in addition to the 12 animals used as mnemonics for the system at large (which has been popularized to the world at large). What's more is that it was also correlated to cardinal directions, the seasons, and even the 12 traditional Chinese units of time which form two-hour periods as opposed to the 60 min. hour increment used in Western society. 

Colloquially, the twelve branches may be referred to as ねうしとらう, which are the first five signs. 

※In addition to the directions listed above, northwest is 戌亥・乾（いぬい）, northeast is 丑寅・艮（うしとら）, southeast is 辰巳・巽（たつみ）, and southwest is 未申・坤（ひつじさる）．The secondary Kanji for each indicate the direction sense of the words. 
※Regarding Kanji usage, though the animals which correspond to each branch are written normally in the parentheses to the right of the English translations, the Kanji for the branches themselves should be used when referring to the year of that animal. In Japanese, you take the KUN reading and follow it with ～どし. Thus, the Year of the Ox would be 丑年（うしどし). It is NOT be written as 牛年

※The animals of the 12 branches are referred to fully as 十二生肖. The exact animals are minutely different than those used in China.
※The 十二時辰 all have names. If you read historical novels, you will come across these terms, but you'll also see "Branch (KUN reading) + の刻（こく）" used as well. Thus, 酉の刻 ＝ 日入. 

※The start of the lunar year does not correspond with the Gregorian calendar as it is based on the lunar calendar which we have yet to cover. However, because the Earthly Branches are tied to them, they are listed for easy reference above. 

※人定 is read as にんじょう.

※You may notice that there are two ways to make specific cardinal directions. In the examples above, the first word corresponds to the modern terms which are in line with Western terminology and the second word is in line with how the same direction was perceived in antiquated Chinese society (inherited into Japanese). 

The 60 Years of the Sexagenary Cycle

Though a lot more can be said about what the Heavenly Stems and Earthly Branches signify, to understand how the calendar itself works, we need to know how they combine to get the names of the 60 years in a cycle. In Japanese society, this is the most significant takeaway. Without further adieu, to aid in understanding, the chart below will start with the last year of the 20th century in which the starting point of the sexagenary cycle began. 

The start of the current sexagenary cycle began in 1984 AD. 

※The ON readings are heavily used in the names of historical events which utilize the sexagenary cycle. However, because of the relatively high frequency of homophonous combinations, in the spoken language, the KUN readings are used to avoid such ambiguity. You may notice that for all KUN readings in which the Heavenly Branch ends in /to/, the particle の is inserted in between the name of the branch and the stem. This is customary and not altered by speakers. 

Months in the Sexagenary Cycle

As hinted at earlier, the sexagenary cycle is also extended to months and days. However, this function has far more influence in traditional Chinese astrology than day-to-day date formation. As there are 12 months in a year and because there are 12 stems, each stem corresponds to the same month. The difference between counting months versus years is that the cycle repeats every five years because of how there are 10 branches to utilize. 

In the chart below, the first column indicates how to convert a month from the Gregorian calendar into the sexagenary cycle by using the final digit of the year. So, for August, 2021, the month would be 丁酉. 

※All of these words are followed by ～月 to disambiguate them from being interpreted in a year or day context. Each word has an ON reading and a KUN reading. You use the same readings as before, but for "month," 月 is read as ゲツ for the Sino-Japanese terms and as のつき for the native terms. 

※It is also possible to not specify the stem and just refer to the sexagenary months with the branches. The means of reading these shortened names is the same. Thus, 寅月 is either read as インゲツ or とらのつき. Only one point of ambiguity exists, which is that 卯月 conflates with the traditional native names for the months of the lunisolar calendar. In contexts of the sexagenary cycle, it refers to Month 2 of the lunisolar calendar, but in contexts of the Japanese version of the lunisolar calendar, it refers to Month 4. To disambiguate, it is best to not shorten the 2nd month of the sexagenary cycle in this way, but if one does, it may still be read as ウゲツ as the etymology is completely separate--卯 referring to "rabbit" whereas the /u/ in the native word 卯月（うづき）derives from an Old Japanese morpheme /uka/ from a verb meaning "to receive" seen in the name of the Goddess of Nature in Shintoism (who was briefly mentioned earlier). 

In Modern Japan, the definition of a month has essentially been replaced with the solar calendar of the Gregorian calendar. However, disregarding the actual starts of the months, the order of the months of the sexagenary cycle still follow the lunisolar calendar.

Days in the Sexagenary Cycle

The method of using the 干支 to count days is referred to as 干支紀日法, and this process has existed since Oracle Bone script was in use. The math for counting the days is the same as counting years. There are 10 branches. If you multiply this by 3, you get 30 days. Then, by combining them with the 12 branches in the same combinations as for the years, you get a repeating cycle that starts over every 60 days (2 months). 

Of course, there would have to be a first day for this system. That day would be 甲子 and it's thought that day keeping has been done for the last 3,000 years. Thanks to numerous references of this system throughout history, it's possible to know what day today is in this system. January 27, 2019, for instance is an example of  甲子. Formulas exist to convert a sexagenary date to the Gregorian calendar, but as the math is beyond the capability of average mental math, people largely rely on calendars with this information already compiled. If you would like to know the current day's sexagenary cycle, simply use a resource such as this. 

It is also possible to see the days of the sexagenary cycle referenced with just the 12 branches, in which case each "day" occurs at least twice a month. For instance, the day of the tiger (寅の日) has occurred twice in August 2021 (of the Western Calendar) on the 10th and the 22nd. To reference these days in Japanese, you take the KUN reading of the corresponding branch and add ～の日.

※Then, if you wanted to include the ten branches, you would still use the KUN readings from before. Thus, the first day of the sexagenary cycle would be 甲子の日（きのえのひ）. Though it would be possible to read these words in their ON readings with 日（ニチ）, this is not used in practice. 

Our coverage of the Japanese lunisolar calendar will be brief as how it works is largely the same as the Chinese lunisolar calendar. The greatest difference is where a month begins and ends, but the differences in calculations are marginal at best. 

The Japanese lunisolar calendar, known as 天保壬寅元暦（てんぽうじんいんげん） or 天保暦（てんぽうれき） for short, underwent reform in 1844 AD to revile the calculations that the Western world was implementing. The calculation of the Earth's orbit around the Sun was 365.24219 days, making it even more accurate than the Gregorian calendar.

In this system, the start of the new month is demarcated by the new moon, which happens every other 29-30 days.  There are 24 solar terms known as the 二十四節気, which are equally divided by solar longitude rather than time. It was this reform to the calendar that makes it differ from the Chinese lunisolar calendar used in the sexagenary calendar from earlier, but it was also this reform that hastened the abandoning of the system. 

In this system, occasionally leap months need to be inserted 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, and the exact location is chosen to be where none of the twelve solar terms used to determine the months of the year (whose names we learned earlier) exist. 

In previous calendars, hours, days, and months were of uniform length, but under this calendar, the length of time increments was now based on solar longitude, which is subject to change as the Earth's orbit is not perfectly circular. This calendar also did not account for the situation in which there is more than one month not containing a 中気. Generally speaking, though, the first month of this lunisolar calendar is around mid-February.

To fully understand the terminology behind this system, you'll need to learn all 24 names for the solar terms and how their start and end dates look like (a topic for a future lesson). Thus, the main difference between the Chinese lunisolar calendar an the Japanese lunisolar calendar is one of terminology. The Chinese version has the entire sexagenary cycle behind it whereas the Japanese version is largely limited to the names of the 24 solar terms (which also happen to be used in China to note the timing of seasons), the native names for the lunisolar months (as opposed to the sexagenary names), and other cultural jargon. 

To calculate what the date would be in this calendar system, try using this convertor. 

The greatest takeaway from this lesson is that the world has an abundance of calendars in use. In English-speaking countries, people may just be aware of the Gregorian calendar as a part of their everyday lives, but in Japan, people are just as attached to the 元号 era system as they are with the Western (Gregorian) calendar.

We also learned briefly about what is meant by solar and lunisolar. As the lunisolar calendar has been officially abandoned in Japan for over a century, its influence continues to wane. Although it is still important to understand this distinction when referencing the sexagenary cycle which is still a culturally influential calendar, having to worry about where to add leap months and when the solar terms of the (Japanese) lunisolar calendar should start and end are not the problems of everyday people anymore--even if the solar terms do appear on everyone's calendars in conjunction with the Western calendar. 

We also learned how Japan made its own two attempts at creating a 'Japanese' solar calendar in the image of the Gregorian calendar by choosing the dates of Emperor Jinmu's ascension in one attempt and the date of the descent of the grandson of the goddess Amaterasu to Japan in the second attempt. 

Our future studies regarding calendars will involve returning to the Japanese lunisolar calendar but from the perspective of the solar terms known as the 二十四節気. To be just as familiar with them as the average Japanese person, you would first need to learn the 24 names and what season they correspond to. Their names indicate a lot about the weather/climate dynamics of that part of the year, which is the most cultural influence they still provide. As for when these periods start and end, as they are not based on equal increments of time, people rely on premade calendars which automatically make the appropriate calculations based on astronomical observations. Though there are 'problematic' situations with the logistics of the calendar, that has yet to pose a real problem to Japanese society. 

Until you are ready to tackle that next challenge, memorizing key 元号 will help you to better appreciate Japanese history, and learning the combinations of the 干支 and what they mean for fortunetelling will enable you to better appreciate how the sexagenary calendar remains influential in not just Japan but now the world.