Calendar Systems of Japan

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.

  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.
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 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
 2 丑 ちゅう うし Ox
 3 寅 いん とら Tiger
 4 卯 ぼう う Rabbit
 5 辰 しん たつ Dragon
 6 巳 し み Snake
 7 午 ご うま Horse
  South南  5th 
 8 未 び ひつじ Goat
 9 申 しん さる Monkey
 10 酉 ゆう とり Rooster 
 11 戌 じゅつ いぬ Dog
 12 亥 がい い Boar

※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. 

 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 丁 戊 己 庚 辛 壬 癸 乙 丙 丁
 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.