Old Japanese dates


Occasionally I read texts on Japanese history and always struggle to figure
out whether the dates are in the old or new system, specifically whether
something like 四月 corresponds to April as in the western calendar or to the
fourth months in the old calendar. In my experience both options are used more
or less randomly.

Is there any way to make sure from the language or are there any other
indications (publication year, type of book,....) which of the two dates is
meant?




I'm not aware of any ironclad rule for this. You can generally assume the old
calendar is used as long as there is a 元号 and it's a pre-幕末 event. For example
[Wikipedia's
guideline](https://ja.wikipedia.org/wiki/Wikipedia:%E8%A1%A8%E8%A8%98%E3%82%AC%E3%82%A4%E3%83%89#.E5.B9.B4.E6.9C.88.E6.97.A5.E3.83.BB.E6.99.82.E9.96.93)
says:

> 和暦においては、太陽暦移行（1873年（明治6年）1月1日）以後は新暦を、それより前は原則として旧暦を用います。

大政奉還 happened on 1867年11月9日 in the Gregorian calendar and 慶応3年10月14日 in the
old calendar. Most articles about 大政奉還 listed
[here](https://kotobank.jp/word/%E5%A4%A7%E6%94%BF%E5%A5%89%E9%82%84-91474)
either silently use the date in the old calendar (i.e. 10月14日) or explicitly
lists the two dates in both systems.

[徳川家重](https://en.wikipedia.org/wiki/Tokugawa_Ieshige) was born on 1712年1月28日
in the Gregorian calendar and 正徳元年12月21日 in the old calendar. However 正徳元年
mostly overlaps AD 1711 in the Gregorian calendar. Then was he born in 1711 or
1712 in 西暦? The result is [the strange discrepancy about his birth
year](https://kotobank.jp/word/%E5%BE%B3%E5%B7%9D%E5%AE%B6%E9%87%8D-104678)
found in various sources. One source says he was born in `1712*`, where this
asterisk is described in the book's [凡例
page](https://kotobank.jp/hanrei/nihonjinmeijiten/01/) as:

>
> 生没年は，西暦年で示しています。和暦年が西暦年と一部一致しない旧暦明治5年12月3日（新暦明治6年1月1日）の太陽暦採用以前については，和暦の年末に西暦年が新しくなる場合，新たな西暦年数を採り「＊」を付けてその旨を明示しています。

But I don't think this symbol is widely used elsewhere.

Another source says he was born in 1711, and says in its [凡例
page](https://kotobank.jp/hanrei/nipponica/01/):

>   2. 西暦と和暦の関係は、厳密に月日まで比定せず、原則として改元年号で示した。
>   3.
> 明治5年（1872）の改暦以前の月日は原則として和暦によった。西暦と和暦には月日において若干のずれがあり、とくに和暦12月は西暦換算で翌年になる場合が多いが、本書では和暦によった。
>

One source even says he was born on 1711年12月21日, which seems highly confusing
(or wrong) to me...

So you'll have to be very cautious when the year is expressed in four digits.
Basically you'll have to figure out the rule of each publication from the
preface or such.




_Japanese people don't care much about it. For example 沖田総司 Souji Okita a
member of 新選組 Shinsen-gumi died in **慶応4年5月30日 = July 19th 1868** , this is
probably your question._

Japanese calendar is confusing. Before the internet, most people forced the
imperial calendar. Now many people found inconvenience and shifting into
western calendar.

**Imperial calendar(元号):** The new period starts with the new emperor. 平成 1989
- 2018, the current emperor told us his abdication on 2019. It is going to be
a new period.

Any documents from Public office are written in this way.e.g Driving License
expire 平成31 and I have no crew because I don't remember year in 元号. My
grandmother was born in 大正15年 hard to count her age because of sum of 平成, 昭和
and 大正, it is very simple to calculate if she could tell us born in 1926. Most
commercial companies no longer use Imperial calendar, Insurance companies,
Bank and Stock companies. They were fed up with the problems became real after
the shift of 平成 new imperial year such as no 昭和105年 and etc. News sometimes
tells us "The new bullet train, the linear motor car" plans to start
commercial drive in year of 30!" (sorry it's strange English but no other way
to tell) So people heard this it comes in a years or 13 years. This is
annoying.

**Lunar calendar 旧暦** : it's different from Chinese calendar and roughly a
month or two late from western calendar, as you know it's based on moon face,
the full moon day is 15日, the new moon is 1日, month ends 29 or 30. This had
been s an official until 明治5年12月2日 = December 31th 1872. **_The installation
of Gregorian calendar in Japan was 1873 January 1st._** So Meiji 5 has 26 days
shorter than other years. Before this happens every documents in Japan were
written in Imperial year and Japanese lunar calendar.

Japanese lunar calendar is somewhat fuzzy. It's very different from Chinese.
In some suburban places, they has been hold ひな祭り(hina-matsuri) March 3th, it
was on the lunar calendar, so they found the way it's roughly a month late
then it'd be held on April 3th.

**Before the Meiji period, it would be the lunar calendar with imperial year
which is very hard to know the accurate date in western calendar.**

FYI:

For year 2017 = 平成/Heisei 29 = 昭和/Showa 92 = 大正/Taisho 106 = 明治/Meiji 150

For Month in modren/old Japanese alias

January １月:睦月(むつき)

February ２月:如月(きさらぎ)

March ３月:弥生(やよい)

April ４月:卯月(うづき)

May ５月:皐月(さつき)

June ６月:水無月(みなづき)

July ７月:文月(ふみづき)

August ８月:葉月(はづき)

September ９月:長月(ながつき)

October 10月:神無月(かんなづき)

November 11月:霜月(しもつき)

December 12月:師走(しわす)

