第338課: Calendar Systems of Japan 日本における紀年法
There are two words for calendar in Japanese: 暦 and カレンダー. The former word is used to refer to either the physical calendar which indicates various things such as sunset/sunrise, events, seasons, tide, etc. or to the means of counting the years, months, and days. On the other hand, カレンダー just refers to physical calendars.
Recording the passage of time may seem easy enough, but the world has many different calendar systems. With that being said, the most obvious fact that can be observed is that the Earth rotates on its access and orbits the Sun. A year, the time it takes for the Earth to make one rotation around the Sun, is approximately every 365-6 days with leap years inserted to account for this orbit not perfectly 365 days. A calendar created by following the rotation of the Sun are called solar calendars (太陽暦). In English-speaking countries, the Western (Gregorian) calendar is an example of a solar calendar, and it is also the most widely used calendar in the world.
Though Year 1 of the Western calendar is based on religious reasons, the calculation for how long a year is remains one of the most accurate calendars in the world, which is why it is used irrespective of its religious ties by the international community.
As for the other calendar systems of the world, they can be divided into three types.
1. A specific year in time is determined to be the starting point (始点), in which all time afterward is accounted. Examples of such systems include the Christian Era, a.k.a, the Western calendar (キリスト紀元), the Hijiri Era, a.k.a, the Islamic calendar (ヒジュラ紀元), the Buddhist calendar (仏滅紀元), the Japanese Imperial Era (神武紀元), and the Human Era (人類紀元). With exception to the last calendar system, the first year of these systems is deemed Year 1.
2. Another form of calendars involves resets that occur with the ascension to power of a new ruler or similar event, such is the case with the 元号 (era name) system used in Japan.
3. Popularized by Chinese culture, the Sexagenary Cycle (干支) is also a calendar system made up of sixty terms (years) in each cycle.
Calendars may also differ as to whether they’re solar calendars (太陽暦) or lunisolar calendars (太陰太陽暦), which affects the demarcation of years and months themselves and not just counting them. This dynamic is separate from the concept of counting the years themselves, so it is plausible for a calendar system to be utilized in both ways. For example, in Japan, the Western Calendar has become the most widely used calendar. However, its implementation was not as simple as changing the Year 5 of the Meiji Period to the Year 1872 when the official change was made. At that time, it was the solar calendar aspect of the Western Calendar that was adopted with the full Gregorian format becoming commonly used after World War II.
The first goal of this lesson is to learn how years are counted in the calendar systems that exist in Japan. Whether something is used as a solar calendar or as a lunisolar calendar is a secondary aspect in that this distinction deals more with the passage of months and seasons. For the most part, we’ll be learning how years, months, and days are counted in these systems, and by doing so, this secondary aspect will become evident.
Our second goal will then be to look specifically how the lunisolar calendar known as 天保暦 has been used in Japan, which will focus mostly on when the months of the lunar year are in comparison to their start dates in the Western calendar.
Lastly, because we are dealing with various date formats, all calendar systems discussed will be compared to the Western Calendar. As such, any date unspecified as being of a different calendar system should be understand as being written in the Western Calendar.
Orthography Note: The purpose of this lesson is to detail the use of calendar systems in Japan and how the ‘date’ is described accordingly in those systems. How numbers themselves are transcribed varies for unrelated reasons. For instance, the difference between transcribing Year 1 as 1年, 一年, or 壱年 or similar orthographical nuancing is covered in the lesson linked here.
The Western Calendar 西暦
The Western Calendar is known in Japan simply as 政略, although it is also technically known throughout the world as the Gregorian calendar (グレゴリオ暦), which is a slightly updated of the Julian calendar ユリウス暦. It was introduced in 1582 AD by Pope Gregory XIII. The average year (平年) is composed of 365 days. Within the span of 400 years, there are 97 leap years (閏年), and in those years there are 366 days. This means the average length of a year is approximately 365.2425 days. In the Julian calendar, the average length of a year was calculated to be 365.25 days. Based on current scientific observation, the average solar year (太陽年) or year of revolution around the Sun (回帰年) is 365.242189572 days. Thus, the accuracy of this improved calendar, which was put in place in 1582 AD, was remarkably precise despite the lack of today’s technology, only being off by 26.821 seconds, the time it likely took you to read this paragraph.
The years are then numbered according to what’s known as the Common Era (西暦紀元・キリスト紀元), which splits history into two parts: BC (before Christ) and AD (after Christ). The association of AD, a contraction of Anno Domini meaning “[the] year of [the] Lord” with the birthyear (生年) of Christ (イエス) is strong in many countries. However, in standard Japanese notation of the Western Calendar, neither AD/BC or the neutral equivalents CE/BCE are generally used. Instead, the formats seen in the chart below are used.
| Year #### BC(E) | Year #### AD/CE |
| (紀元)前ｘｘｘｘ年 | (ｘｘ)ｘｘ年 |
Contraction Notes:
①As indicated in the chart, BC(E) years may be noted with just 前（ぜん） before the year.
②AD/CE years of the 20th and 21st centuries are frequently abbreviated to the last two digits. However, determining what year is meant must be done so in context. For instance, 20年代 may mean “the 20s,” but whether this is in reference in the 1920s or the 2020s is left to context to decide.
1. 紀元前2000年
The Year 2000 BC(E)
2. 2000年
The Year 2000 AD
As alluded to earlier, 1 AD is not 0年 but rather 紀元前1年. Thus, the beginning of time, even though the time immediately preceding the first increment of time would be point 0, that date would be expressed with astronomically large number. The Big Bang is thought to have occurred
Occasionally, to distinguish a date as being from the Western calendar as opposed to another system, 西暦 may be placed before the year.
3. 西暦1865年
Months and Days
Months and days are numbered no differently in Japan with the Western calendar as they are in English speaking countries. Months will have 28-31 days depending on the month. At the start of your Japanese studies, you learned that the names of the months were simply “No. + 月（がつ）.” Japan follows the YEAR/MONTH/DAY format as opposed to the American MONTH/DAY/YEAR format.
4. 2018年7月25日
July 25th, 2018
5. 2021年8月24日
August 24th, 2021
However, Japanese already had a set of traditional names for the months from when it had been using its own lunisolar calendar. Confusingly, though, these names have also had their original meanings corrupted to be interpreted the same way as the solar calendar. A quick way to convert them to the lunisolar calendar is by forwarding the time by two months. So, the lunisolar “January” is the solar calendar’s version of “March,” the start of spring (立春).
| 旧暦の月 | 和風月名 | 由来 |
| 1月 | 睦月（むつき） | The month in which every gets close together–睦ぶ月 for the New Year. |
| 2月 | 如月・衣更着（きさらぎ） | A month in which cold days may still linger, in which case one finds oneself putting on double layers, but spring is beginning to truly getting into full gear. |
| 3月 | 弥生（やよい） | From the Old Japanese adjectival noun いやおい which refers to vegetation growing prolifically. |
| 4月 | 卯月（うづき） | Simplest etymologically being the month in which the 卯の花 (deutzia) buds, but another possibility is that the /u/ derives from the name of the goddess responsible for natur’es blessing, Ukanomitama-no-mikoto (倉稲魂命) . |
| 5月 | 皐月・早月（さつき） | The month in which one begins to sow rice seedlings (早苗). |
| 6月 | 水無月（みなづき・みなつき） | The month in which one brings water to one’s fields. The 無 is simply Ateji for the particle な, which is an archaic attribute marker. |
| 7月 | 文月（ふみづき・ふづき） | Another case of Ateji, this is a contraction of 穂含月（ほふみづき）, the month in which ears of rice are ready for harvest. |
| 8月 | 葉月（はづき・はつき） | The month in which the leaves fall. |
| 9月 | 長月（ながづき・ながつき） | The contraction of 夜長月（よながづき）, this is the month in which the nights are long. |
| 10月 | 神無月（かんなづき） | The month in which all kami of the land gather at the Izumo Grand Shrine, leaving the land also barren of kami. The use of 無 is used both phonetically to represent the ancient particle な as well as to add that last layer of meaning. |
| 11月 | 霜月（しもつき） | The month in which frost falls. |
| 12月 | 師走（しわす） | A contraction of 師馳せ月（しはせづき）, this is the month in which priests ran about hurriedly to perform memorial services for people’s ancestors. |
※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.
The Era Name System 日本の元号
Also known as 和暦 or 邦暦, the practice of counting years based on the reign of emperors/rulers has been widely practiced in East Asia. As for Japan’s own iteration, the first ‘era’ that was ordained was done so by Emperor Kō toku (孝徳天皇) in the Asuka Period (飛鳥時代). This ‘era’ is known as the Taika Era (大化).
The use of the word 時代 in relation to any specific 元号 is slightly arbitrary. Modern eras are frequently referred to as 時代, but not all 元号 are treated this way as the majority did not last for decades. Some, just as was the case of the Taika Era, refer to only a number of years, and in those cases, the word 時代 wouldn’t be fitting. Either the 元号 in reference to a large period of time itself (ex. the Asuka Period) or the use of the suffix ～期 would be more appropriate.
Ever since the Japanese system of 元号 was enacted in 645 AD, there have been 248 different eras. During the Period of the Northern and Southern Dynasties (南北朝時代), there were two competing imperial lines, which resulted in overlap that contributes to this number. Additionally, though the system began in 645 AD, up until 701 AD, not all emperors instituted a proper 元号. Furthermore, due to Japan’s long history of internal conflict and instability, there were also several colloquial era names unaligned with the ’emperor-centric’ convention that were passed down in certain communities; however, for the purpose of this discussion, only the traditionally recognized and historically significant 248 era names will be listed.
When a new emperor ascends the throne, the era changes at that moment, a process which is referred to as 改元. This results in the year in question having two valid era names. For instance, 2019 AD was both Year 31 of the Heisei Era (平成時代31年) as well as Year 1 of the Reiwa Era (令和時代元年). Year 1 of any era is referred to as the 元年 of that year, this term being interchangeable with 1年. The convention of changing the era with each reign of an emperor only became codified in 1868 AD. Before then, various other reasons had also been used to bring about a new era name.
To facilitate seeing the many era names that have existed, each chart below corresponds to a specific period in Japanese history. For when there were two naming conventions based on either the northern or the southern dynasty during which the imperial line was divided, those era names will be contrasted in the same chart so that the charts may continue in chronological order.
※Though the first true era name begins with 大化 starting at 645 AD, there is a means of retroactively applying ‘era names’ based on the names of the emperors that reigned all the way back to the first emperor of Japan, Emperor Jinmu, who is said to have 660 BC. These additions to the 和暦 will be listed at the end.
Era Names of the Asuka Period 飛鳥時代の元号
| 元号名 | 読み | 期間（西暦） | 元号名 | 読み | 期間（西暦） |
| 大化 | たいか | 645~650 AD | 白雉 | はくち | 650~654 AD |
| 朱鳥 | しゅちょう | 686 AD | 大宝 | たいほう | 701~704 AD |
| 慶雲 | けいうん | 704-708 AD | 和銅 | わどう | 708-715 AD |
Era Names of the Nara Period 奈良時代の元号
| 元号名 | 読み | 期間（西暦） | 元号名 | 読み | 期間（西暦） |
| 霊亀 | れいき | 715-717 AD | 養老 | ようろう | 717-724 AD |
| 神亀 | じんき | 724-729 AD | 天平 | てんぴょう | 729-749 AD |
| 天平感宝 | てんぴょうかんぽう | 749 AD | 天平勝宝 | てんぴょうしょうほう | 749-757 AD |
| 天平宝字 | てんぴょうほうじ | 757-765 AD | 天平神護 | てんぴょうじんご | 765-767 AD |
| 神護景雲 | てんぴょうけいうん | 767-770 AD | 宝亀 | ほうき | 770-781 AD |
| 天応 | てんおう | 781-782 AD | 延暦 | えんりゃく | 782-806 AD |
Era Names of the Heian Period 平安時代の元号
| 元号名 | 読み | 期間（西暦） | 元号名 | 読み | 期間（西暦） |
| 大同 | だいどう | 806-810 AD | 弘仁 | こうにん | 810-824 AD |
| 天長 | てんちょう | 824-834 AD | 承和 | じょうわ | 834-848 AD |
| 嘉祥 | かしょう | 848-851 AD | 仁寿 | にんじゅ | 851-854 AD |
| 斉衡 | さいこう | 854-857 AD | 天安 | てんあん | 857-859 AD |
| 貞観 | じょうがん | 859-877 AD | 元慶 | がんぎょう | 877-885 AD |
| 仁和 | にんな | 885-889 AD | 寛平 | かんぴょう | 889-898 AD |
| 昌泰 | しょうたい | 898-901 AD | 延喜 | えんぎ | 901-923 AD |
| 延長 | えんちょう | 923-931 AD | 承平 | じょうへい | 931-938 AD |
| 天慶 | てんぎょう | 938-947 AD | 天暦 | てんりゃく | 947-957 AD |
| 天徳 | てんとく | 957-961 AD | 応和 | おうわ | 961-964 AD |
| 康保 | こうほう | 964-968 AD | 安和 | あんな | 968-970 AD |
| 天禄 | てんろく | 970-974 AD | 天延 | てんえん | 974-976 AD |
| 貞元 | じょうげん | 976-978 AD | 天元 | てんげん | 978-983 AD |
| 永観 | えいかん | 983-985 AD | 寛和 | かんな | 985-987 AD |
| 永延 | えいえん | 987-989 AD | 永祚 | えいそ | 989-990 AD |
| 正暦 | しょうりゃく | 990-995 AD | 長徳 | ちょうとく | 995-999 AD |
| 長保 | ちょうほう | 999-1004 AD | 寛弘 | かんこう | 1014-1013 AD |
| 長和 | ちょうわ | 1013-1017 AD | 寛仁 | かんにん | 1017-1021 AD |
| 治安 | じあん | 1021-1024 AD | 万寿 | まんじゅ | 1024-1028 AD |
| 長元 | ちょうげん | 1028-1037 AD | 長暦 | ちょうりゃく | 1037-1040 AD |
| 長久 | ちょうきゅう | 1040-1044 AD | 寛徳 | かんとく | 1044-1046 AD |
| 永承 | えいしょう | 1046-1053 AD | 天喜 | てんぎ | 1053-1058 AD |
| 康平 | こうへい | 1058-1065 AD | 治暦 | じりゃく | 1065-1069 AD |
| 延久 | えんきゅう | 1069-1074 AD | 承保 | じょうほう | 1074-1077 AD |
| 承暦 | じょうりゃく | 1077-1081 AD | 永保 | えいほう | 1081-1084 AD |
| 応徳 | おうとく | 1084-1087 AD | 寛治 | かんじ | 1087-1095 AD |
| 嘉保 | かほう | 1095-1097 AD | 永長 | えいちょう | 1097-1097 AD |
| 承徳 | じょうとく | 1097-1099 AD | 康和 | こうわ | 1099-1104 AD |
| 長治 | ちょうじ | 1104-1106 AD | 嘉承 | かしょう | 1106-1108 AD |
| 天仁 | てんにん | 1108-1110 AD | 天永 | てんえい | 1110-1113 AD |
| 永久 | えいきゅう | 1113-1118 AD | 元永 | げんえい | 1118-1120 AD |
| 保安 | ほうあん | 1120-1124 AD | 天治 | てんじ | 1124-1126 AD |
| 大治 | だいじ | 1126-1131 AD | 天承 | てんしょう | 1131-1132 AD |
| 長承 | ちょうしょう | 1132-1135 AD | 保延 | ほうえん | 1135-1141 AD |
| 永治 | えいじ | 1141-1142 AD | 康治 | こうじ | 1142-1144 AD |
| 天養 | てんよう | 1144-1145 AD | 久安 | きゅうあん | 1145-1151 AD |
| 仁平 | にんぺい | 1151-1154 AD | 久寿 | きゅうじゅ | 1154-1156 AD |
| 保元 | ほうげん | 1156-1159 AD | 平治 | へいじ | 1159-1160 AD |
| 永暦 | えいりゃく | 1160-1161 AD | 応保 | おうほう | 1161-1163 AD |
| 長寛 | ちょうかん | 1163-1165 AD | 永万 | えいまん | 1165-1166 AD |
| 仁安 | にんあん | 1166-1169 AD | 嘉応 | かおう | 1169-1171 AD |
| 承安 | じょうあん | 1171-1175 AD | 安元 | あんげん | 1175-1177 AD |
| 治承※ | じしょう | 1177-1181 AD | 養和※ | ようわ | 1181-1182 AD |
| 寿永※ | じゅえい | 1182-1184 AD | 元暦※ | げんりゃく | 1184-1185 AD |
※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
| 元号名 | 読み | 期間（西暦） | 元号名 | 読み | 期間（西暦） |
| 文治 | ぶんじ | 1185-1190 AD | 建久 | けんきゅう | 1190-1199 AD |
| 正治 | しょうじ | 1199-1201 AD | 建仁 | けんにん | 1201-1204 AD |
| 元久 | げんきゅう | 1204-1206 AD | 建永 | けんえい | 1206-1207 AD |
| 承元 | じょうげん | 1207-1211 AD | 建暦 | けんりゃく | 1211-1214 AD |
| 建保 | けんぽう | 1214-1219 AD | 承久 | じょうきゅう | 1219-1222 AD |
| 貞応 | じょうおう | 1222-1224 AD | 元仁 | げんにん | 1224-1225 AD |
| 嘉禄 | かろく | 1225-1228 AD | 安貞 | あんてい | 1228-1229 AD |
| 寛喜 | かんぎ | 1229-1232 AD | 貞永 | じょうえい | 1232-1233 AD |
| 天福 | てんぷく | 1233-1234 AD | 文暦 | ぶんりゃく | 1234-1235 AD |
| 嘉禎 | かてい | 1235-1238 AD | 暦仁 | りゃくにん | 1238-1239 AD |
| 延応 | えんおう | 1239-1240 AD | 仁治 | にんじ | 1240-1243 AD |
| 寛元 | かんげん | 1243-1247 AD | 宝治 | ほうじ | 1247-1249 AD |
| 建長 | けんちょう | 1249-1256 AD | 康元 | こうげん | 1256-1257 AD |
| 正嘉 | しょうか | 1257-1259 AD | 正元 | しょうげん | 1259-1260 AD |
| 文応 | ぶんおう | 1260-1261 AD | 弘長 | こうちょう | 1261-1264 AD |
| 文永 | ぶんえい | 1264-1275 AD | 建治 | けんじ | 1275-1278 AD |
| 弘安 | こうあん | 1278-1288 AD | 正応 | しょうおう | 1288-1293 AD |
| 永仁 | えいにん | 1293-1299 AD | 正安 | しょうあん | 1299-1302 AD |
| 乾元 | けんげん | 1302-1303 AD | 嘉元 | かげん | 1303-1307 AD |
| 徳治 | とくじ | 1307-1308 AD | 延慶 | えんきょう | 1308-1311 AD |
| 応長 | おうちょう | 1311-1312 AD | 正和 | しょうわ | 1312-1317 AD |
| 文保 | ぶんぽう | 1317-1319 AD | 元応 | げんおう | 1319-1321 AD |
| 元亨 | げんこう | 1321-1324 AD | 正中 | しょうちゅう | 1324-1326 AD |
| 嘉暦 | かりゃく | 1326-1329 AD | 元徳※ | げんとく | 1329-1331/1332 AD |
| 元弘※ | げんこう | 1331-1334 AD | 正慶※ | しょうけい | 1332-1333 AD |
※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).
| 南朝の元号 | 読み | 期間（西暦） | 北朝の元号 | 読み | 期間（西暦） |
| 延元 | えんげん | 1336-1340 AD | 暦応 | りゃくおう | 1338-1342 AD |
| 興国 | こうこく | 1340-1347 AD | 康永 | こうえい | 1342-1345 |
| 正平 | しょうへい | 1347-1370 AD | 貞和 | じょうわ | 1345-1350 AD |
| 建徳 | けんとく | 1370-1372 AD | 観応 | かんのう | 1350-1352 AD |
| 文中 | ぶんちゅう | 1372-1375 AD | 文和 | ぶんな | 1352-1356 AD |
| 天授 | てんじゅ | 1375-1381 AD | 延文 | えんぶん | 1356-1361- AD |
| 弘和 | こうわ | 1381-1384 AD | 康安 | こうあん | 1361-1362 AD |
| 元中 | げんちゅう | 1384-1392 AD | 貞治 | じょうじ | 1362-1368 AD |
| 応安 | おうあん | 1368-1375 AD | |||
| 永和 | えいわ | 1375-1379 AD | |||
| 康暦 | こうりゃく | 1379-1381 AD | |||
| 永徳 | えいとく | 1381-1384 AD | |||
| 至徳 | しとく | 1384-1387 AD | |||
| 嘉慶 | かけい | 1387-1389 AD | |||
| 康応 | こうおう | 1389-1390 AD | |||
| 明徳 | めいとく | 1390-1394 AD |
※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.
| 元号名 | 読み | 期間（西暦） | 元号名 | 読み | 期間（西暦） |
| 応永 | おうえい | 1394-1428 AD | 正長 | しょうちょう | 1428-1429 AD |
| 永享 | えいきょう | 1429-1441 AD | 嘉吉 | かきつ | 1441-1444 AD |
| 文安 | ぶんあん | 1444-1449 AD | 宝徳 | ほうとく | 1449-1452 AD |
| 享徳 | きょうとく | 1452-1455 AD | 康正 | こうしょう | 1455-1457 AD |
| 長禄 | ちょうろく | 1457-1461 AD | 寛正 | かんしょう | 1461-1466 AD |
| 文正 | ぶんしょう | 1466-1467 AD |
Era Names of the Sengoku Period 戦国時代の元号
| 元号名 | 読み | 期間（西暦） | 元号名 | 読み | 期間（西暦） |
| 応仁 | おうにん | 1467-1469 AD | 文明 | ぶんめい | 1469-1487 AD |
| 長享 | ちょうきょう | 1487-1489 AD | 延徳 | えんとく | 1489-1492 AD |
| 明応 | めいおう | 1492-1501 AD | 文亀 | ぶんき | 1501-1504 AD |
| 永正 | えいしょう | 1504-1521 AD | 大永 | たいえい | 1521-1528 AD |
| 享禄 | きょうろく | 1528-1532 AD | 天文 | てんぶん | 1532-1555 AD |
| 弘治 | こうじ | 1555-1558 AD | 永禄 | えいろく | 1558-1570 AD |
| 元亀 | げんき | 1570-1573 AD |
Era Names of the Azuchi-Momoyama Period 安土桃山時代の元号
| 元号名 | 読み | 期間（西暦） | 元号名 | 読み | 期間（西暦） |
| 天正 | てんしょう | 1573-1593 AD | 文禄 | ぶんろく | 1593-1596 AD |
| 慶長 | けいちょう | 1596-1615 AD |
Era Names of the Edo Period 江戸時代の元号
| 元号名 | 読み | 期間（西暦） | 元号名 | 読み | 期間（西暦） |
| 元和 | げんな | 1615-1624 AD | 寛永 | かんえい | 1624-1645 AD |
| 正保 | しょうほう | 1645-1648 AD | 慶安 | けいあん | 1648-1652 AD |
| 承応 | じょうおう | 1652-1655 AD | 明暦 | めいれき | 1655-1658 AD |
| 万治 | まんじ | 1658-1661 AD | 寛文 | かんぶん | 1661-1673 AD |
| 延宝 | えんぽう | 1673-1681 AD | 天和 | てんな | 1681-1684 AD |
| 貞享 | じょうきょう | 1684-1688 AD | 元禄 | げんろく | 1688-1704 AD |
| 宝永 | ほうえい | 1704-1711 AD | 正徳 | しょうとく | 1711-1716 AD |
| 享保 | きょうほう | 1716-1736 AD | 元文 | げんぶん | 1736-1741 AD |
| 寛保 | かんぽう | 1741-1744 AD | 延享 | えんきょう | 1744-1748 AD |
| 寛延 | かんえん | 1748-1751 AD | 宝暦 | ほうれき | 1751-1764 AD |
| 明和 | めいわ | 1764-1772 AD | 安永 | あんえい | 1772-1781 AD |
| 天明 | てんめい | 1781-1789 AD | 寛政 | かんせい | 1789-1801 AD |
| 享和 | きょうわ | 1801-1804 AD | 文化 | ぶんか | 1804-1818 AD |
| 文政 | ぶんせい | 1818-1831 AD | 天保 | てんぽう | 1831-1845 AD |
| 弘化 | こうか | 1845-1848 AD | 嘉永 | かえい | 1848-1855 AD |
| 安政 | あんせい | 1855-1860 AD | 万延 | まんえん | 1860-1861 AD |
| 文久 | ぶんきゅう | 1861-1864 AD | 元治 | げんじ | 1864-1865 AD |
| 慶応 | けいおう | 1865-1868 AD |
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.
| 元号名 | 読み | 期間（西暦） | 元号名 | 読み | 期間（西暦） |
| 明治 | めいじ | 1868-1912 AD | 大正 | たいしょう | 1912-1926 AD |
| 昭和 | しょうわ | 1926-1989 AD | 平成 | へいせい | 1989-2019 AD |
| 令和 | れいわ | 2019-2021 AD |
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.
| 年号 | 読み | 期間（西暦） | 年号 | 読み | 期間（西暦） |
| 神武（天皇） | じんむ | 660-581 BC | 綏靖（天皇） | すいぜい | 581-548 BC |
| 安寧（天皇） | あんねい | 548-510 BC | 懿徳 （天皇） | いとく | 510-475 BC |
| 孝昭（天皇） | こうしょう | 475-392 BC | 考安（天皇） | こうあん | 392-290 BC |
| 孝霊（天皇） | こうれい | 290-214 BC | 孝元（天皇） | こうげん | 214-157 BC |
| 開化（天皇） | かいか | 157-97 BC | 崇神（天皇） | すじん | 97-29 BC |
| 垂仁（天皇） | すいにん | 29 BC-71 AD | 景行（天皇） | けいこう | 71-131 AD |
| 成務（天皇） | せいむ | 131-192 AD | 仲哀（天皇） | ちゅうあい | 192-201 AD |
| 神功皇后摂政 | じんぐうこうぐうせっしょう | 201-270 AD | 応神（天皇） | おうじん | 270-313 AD |
| 仁徳（天皇） | にんとく | 313-400 AD | 履中（天皇） | りちゅう | 400-406 AD |
| 反正（天皇） | はんぜい | 406-412 AD | 允恭（天皇） | いんぎょう | 412-454 AD |
| 安康（天皇） | あんこう | 454-457 AD | 雄略（天皇） | ゆうりゃく | 457-480 AD |
| 清寧（天皇） | せいねい | 480-485 AD | 顕宗（天皇） | けんぞう | 485-488 AD |
| 仁賢（天皇） | にんけん | 488-499 AD | 武烈（天皇） | ぶれつ | 499-507 AD |
| 継体（天皇） | けいたい | 507-534 AD | 安閑（天皇） | あんかん | 534-536 AD |
| 宣化（天皇） | せんか | 536-540 AD | 欽明（天皇） | きんめい | 540-572 AD |
| 敏達（天皇） | びだつ | 572-586 AD | 用明（天皇） | ようめい | 586-588 AD |
| 崇峻（天皇） | すしゅん | 588-592 AD | 推古（天皇） | すいこ | 592-629 AD |
| 舒明（天皇） | じょめい | 629-642 AD | 皇極（天皇） | こうぎょく | 642-645 AD |
※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 Imperial Era & Divine Descent Calendars 神武紀元・天孫紀元
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.
- 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.
- 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.
| 西暦 | 元号 | 神武紀元 | 天孫紀元 |
| 1945 AD | 昭和20年 | 皇紀2605年 | 天孫紀元1795068年 |
| 2000 AD | 平成12年 | 皇紀2660年 | 天孫紀元1795133年 |
| 2021 AD | 令和3年 | 皇紀2681年 | 天孫紀元1795154年 |
Stems-and-Branches (Sexagenary Cycle) 干支
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.
| # | 十干 | 音読み | 訓読み | 陰陽 | 五行 | 五星 | 五方 |
| 1/A | 甲 | こう | きのえ（→木の兄） | 陽 (yang) | Wood | Jupiter | East |
| 2/B | 乙 | おつ | きのと（→木の弟） | 陰 (yin) | Wood | Jupiter | East |
| 3/C | 丙 | へい | ひのえ（→火の兄） | 陽 (yang) | Fire | Mars | South |
| 4/D | 丁 | てい | ひのと（→火の弟） | 陰 (yin) | Fire | Mars | South |
| 5/E | 戊 | ぼ | つちのえ（→土の兄） | 陽 (yang) | Earth | Saturn | Center |
| 6/F | 己 | き | つちのと（→土の弟） | 陰 (yin) | Earth | Saturn | Center |
| 7/G | 庚 | こう | かのえ（→金の兄） | 陽 (yang) | Metal | Venus | West |
| 8/H | 辛 | しん | かのと（→金の弟） | 陰 (yin) | Metal | Venus | West |
| 9/I | 壬 | じん | みずのえ（→水の兄） | 陽 (yang) | Water | Mercury | North |
| 10/J | 癸 | き | みずのと（→水の弟） | 陰 (yin) | Water | Mercury | North |
※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.
| ＃ | 字 | 音 | 訓 | 生肖 | 時辰 | 方角 | 月（陰暦） |
| 1 | 子 | し | ね | Rat 鼠 | 0:00~1:59 夜半 | North 北 | 11th |
| 2 | 丑 | ちゅう | うし | Ox 牛 | 2:00~3:59 鶏鳴 | North-northeast 北北東～ 北東微北 | 12th |
| 3 | 寅 | いん | とら | Tiger 虎 | 4:00~5:59 平旦 | East-northeast 東北東～ 北東微南 | 1st |
| 4 | 卯 | ぼう | う | Rabbit 兎 | 6:00~7:59 日出 | East 東 | 2nd |
| 5 | 辰 | しん | たつ | Dragon 竜 | 8:00~9:59 食時 | East-southeast 東南東～ 南東微北 | 3rd |
| 6 | 巳 | し | み | Snake 蛇 | 10:00~11:59 隅中 | South-southeast 南南東～ 南東微南 | 4th |
| 7 | 午 | ご | うま | Horse 馬 | 12:00~13:59 日中 | South南 | 5th |
| 8 | 未 | び | ひつじ | Goat 羊 | 14:00~15:59 日昳 | South-southwest南南西～ 南西微南 | 6th |
| 9 | 申 | しん | さる | Monkey 猿 | 16:00~17:59 晡時 | West-southwest 西南西～ 南西微北 | 7th |
| 10 | 酉 | ゆう | とり | Rooster 鶏 | 18:00~19:59 日入 | West 西 | 8th |
| 11 | 戌 | じゅつ | いぬ | Dog 犬 | 20:00~21:59 黄昏 | West-northwest 西北西～ 北西微南 | 9th |
| 12 | 亥 | がい | い | Boar 猪 | 22:00~23:59 人定 | North-northwest 北北西～ 北西微北 | 10th |
※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.
| 番号 | 干支 | 読み方 | 干支早見表 |
| 1 | 甲子 | コウシ・カッシきのえね | 1984 AD |
| 2 | 乙丑 | イッチュウきのとのうし | 1985 AD |
| 3 | 丙寅 | ヘイインひのえとら | 1986 AD |
| 4 | 丁卯 | テイボウひのとのう | 1987 AD |
| 5 | 戊辰 | ボシンつちのえたつ | 1988 AD |
| 6 | 己巳 | キシつちのとのみ | 1989 AD |
| 7 | 庚午 | コウゴかのえうま | 1990 AD |
| 8 | 辛未 | シンビ かのとのひつじ | 1991 AD |
| 9 | 壬申 | ジンシンみずのえさる | 1992 AD |
| 10 | 癸酉 | キユウみずのとのとり | 1993 AD |
| 11 | 甲戌 | コウジュツ | 1994 AD |
| 12 | 乙亥 | イツガイきのとのい | 1995 AD |
| 13 | 丙子 | ヘイシひのえね | 1996 AD |
| 14 | 丁丑 | テイチュウひのとのうし | 1997 AD |
| 15 | 戊寅 | ボインつちのえとら | 1998 AD |
| 16 | 己卯 | キボウつちのとのう | 1999 AD |
| 17 | 庚辰 | コウシンかのえたつ | 2000 AD |
| 18 | 辛巳 | シンシかのとのみ | 2001 AD |
| 19 | 壬午 | ジンゴみずのえうま | 2002 AD |
| 20 | 癸未 | キビみずのとのひつじ | 2003 AD |
| 21 | 甲申 | コウシンきのえさる | 2004 AD |
| 22 | 乙酉 | イツユウきのとのとり | 2005 AD |
| 23 | 丙戌 | ヘイジュツひのえいぬ | 2006 AD |
| 24 | 丁亥 | テイガイひのとのい | 2007 AD |
| 25 | 戊子 | ボシつちのえね | 2008 AD |
| 26 | 己丑 | キチュウつちのとのうし | 2009 AD |
| 27 | 庚寅 | コウインかのえとら | 2010 AD |
| 28 | 辛卯 | シンボウかのとのう | 2011 AD |
| 29 | 壬辰 | ジンシンみずのえたつ | 2012 AD |
| 30 | 癸巳 | キシみずのとみ | 2013 AD |
| 31 | 甲午 | コウゴきのえうま | 2014 AD |
| 32 | 乙未 | イツビきのとのひつじ | 2015 AD |
| 33 | 丙申 | ヘイシンひのえさる | 2016 AD |
| 34 | 丁酉 | テイユウひのとのとり | 2017 AD |
| 35 | 戊戌 | ボジュツつちのえいぬ | 2018 AD |
| 36 | 己亥 | キガイつちのとのい | 2019 AD |
| 37 | 庚子 | コウシかのえね | 2020 AD |
| 38 | 辛丑 | シンチュウかのとのうし | 2021 AD |
| 39 | 壬寅 | ジンインみずのえとら | 2022 AD |
| 40 | 癸卯 | キボウみずのとのう | 2023 AD |
| 41 | 甲辰 | コウシンきのえたつ | 2024 AD |
| 42 | 乙巳 | イッシきのとのみ | 2025 AD |
| 43 | 丙午 | ヘイゴひのえうま | 2026 AD |
| 44 | 丁未 | テイビひのとのひつじ | 2027 AD |
| 45 | 戊申 | ボシンつちのえさる | 2028 AD |
| 46 | 己酉 | キユウ つちのとのとり | 2029 AD |
| 47 | 庚戌 | コウジュツかのえいぬ | 2030 AD |
| 48 | 辛亥 | シンガイかのとのい | 2031 AD |
| 49 | 壬子 | ジンシみずのえね | 2032 AD |
| 50 | 癸丑 | キチュウみずのとのうし | 2033 AD |
| 51 | 甲寅 | コウインきのえとら | 2034 AD |
| 52 | 乙卯 | イツボウきのとのう | 2035 AD |
| 53 | 丙辰 | ヘイシンひのえたつ | 2036 AD |
| 54 | 丁巳 | テイシひのとのみ | 2037 AD |
| 55 | 戊午 | ボゴつちのえうま | 2038 AD |
| 56 | 己未 | キビつちのとのひつじ | 2039 AD |
| 57 | 庚申 | 庚申 かのえさる | 2040 AD |
| 58 | 辛酉 | シンユウかのとのとり | 2041 AD |
| 59 | 壬戌 | ジンジュツみずのえいぬ | 2042 AD |
| 60 | 癸亥 | キガイみずのとのい | 2043 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.
| 西暦 …# | １月 | ２月 | ３月 | ４月 | ５月 | ６月 | ７月 | ８月 | ９月 | １０月 | １１月 | １２月 |
| 4, 9 | 丙寅 | 丁卯 | 戊辰 | 己巳 | 庚午 | 辛未 | 壬申 | 癸酉 | 甲戌 | 乙亥 | 丙子 | 丁丑 |
| 5, 0 | 戊寅 | 己卯 | 庚辰 | 辛巳 | 壬午 | 癸未 | 甲申 | 乙酉 | 丙戌 | 丁亥 | 戊子 | 己丑 |
| 6, 1 | 庚寅 | 辛卯 | 壬辰 | 癸巳 | 甲午 | 乙未 | 丙申 | 丁酉 | 戊戌 | 己亥 | 庚子 | 辛丑 |
| 7, 2 | 壬寅 | 癸卯 | 甲辰 | 乙巳 | 丙午 | 丁未 | 戊申 | 己酉 | 庚戌 | 辛亥 | 壬子 | 癸丑 |
| 8, 3 | 甲寅 | 乙卯 | 丙辰 | 丁巳 | 戊午 | 己未 | 庚申 | 辛酉 | 壬戌 | 癸亥 | 甲子 | 乙丑 |
※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.
| 日の十二支 | 読み |
| 子の日 | ねのひ |
| 丑の日 | うしのひ |
| 寅の日 | とらのひ |
| 卯の日 | うのひ |
| 辰の日 | たつのひ |
| 巳の日 | みのひ |
| 午の日 | うまのひ |
| 未の日 | ひつじのひ |
| 申の日 | さるのひ |
| 酉の日 | とりのひ |
| 戌の日 | いぬのひ |
| 亥の日 | いのひ |
※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.
The Japanese Lunisolar Calendar 天保暦
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.
In Conclusion… 最後に…
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.