Japanese Date Format

In Japanese, dates are written in year, month, day order (year first, day last), e.g. ２０００年１２月３１日 means year 2000, month 12, day 31, therefore 11/10/09 would be year 2011, month 10 (October), day 9. This is different from the date format typically used in English-speaking countries. Compare:

Language	Date format	Spoken
Japanese	YYYY-MM-DD 2000/12/31	ni-sen-nen, juu-ni-gatsu, san-juu-ichi-nichi ２０００年１２月３１日 Year 2000, month 12, day 31.
British English	DD-MM-YYYY 31/12/2000	Thirty-first of December, 2000. 31st of December, 2000.
American English	MM-DD-YYYY 12/31/2000	December thirty-first, 2000. December 31st, 2000.

Besides the order, the way Japanese dates are written also has some other peculiarities that we'll see through this article.

Source: japanesewithanime.com (CC BY-SA 4.0)

• Usage
  • Separators
  • Kanji Numbers
  • Kanji Digits
  • Partial Dates
  • Japanese Eras Instead of Gregorian Year
  • Parentheses After Date
  • X's, Circles, and Triangles in Dates
  • Vocabulary
    • How to Say the Words for Years, Months, and Days
    • Interrogatives
    • Date Ranges
    • Cyclic Dates
    • ～号
  • Commemorative Dates Based on Wordplay
• Why The Japanese Date Format is Best Date Format
• References

Usage

Dates in Japanese are written and spoken using numbers (ichi, ni, san 一二三) and the counters for "year," "month," and "day," in this order, which respectively would be ~nen ～年, ~gatsu ～月, and ~nichi ～日 (or ~ka 日). For example:

• ni-sen-nen juu-ni-gatsu san-juu-ichi-nichi
  ２０００年１２月３１日
  Year 2000, month 12, day 31.

Separators

Typically, slashes are used to separate the year, month, and day in Japanese dates. Besides slashes, dots and hyphens may be used as well.

Separator	Slashes	Dots	Hyphens
With four-digit year	2000/12/31 2022/02/22 2022/2/22	2000.12.31 2022.02.22 2222.2.22	2000-12-31 2022-02-22 2022-2-22
With two-digit year	00/12/31 22/02/22 22/2/22	00.12.31 22.02.22 22.2.22	00-12-31 22-02-22 22-2-22

Kanji Numbers

It's possible for the number of the year, month, and day of a date to be written as the Japanese word for the number, using kanji, for example, rather than using the number's representation in Arabic numerals.

• ni-sen-nen, juu-ni-gatsu, san-juu-ichi-nichi
  二千年十二月三十一日
  Year two-thousand, month ten-two, day three-ten-one.
  Year 2000, month 12, day 31.

Kanji Digits

It's possible for the number of the year, month, and day of a date to be written using kanji by replacing the digits of the number that would be written using Arabic numerals by the equivalent kanji. There are kanji for the numbers 1 to 9 (一二三四五六七八九), but not for 0, so a circle (small ○ or large ◯) is used for 0 instead, which may be read out loud as maru 丸, "circle."

• ni-maru-maru-maru-nen ichi-ni-gatsu san-ichi-nichi
  二◯◯◯年一二月三一日
  Year two-zero-zero-zero, month one-two, day three-one.
  Year 2000, month 12, day 31.

Partial Dates

Dates don't necessarily need to include year, month, and day. Some dates are only year and month, some are only month and day. For example:

• jyuu-gatsu san-jyuu-ichi-nichi
  １０月３１日
  10/31. (slash separator)
  10.31. (dot separator.)
  Month 10, day 31.
  31st of October.
  Date of Halloween.
• jyuu-ni-gatsu ni-jyuu-go-nichi
  １２月２５日
  12/25. (slash separator.)
  12.25. (dot separator.)
  Month 12, day 25.
  25th of December.
  Date of Christmas.

Japanese Eras Instead of Gregorian Year

Sometimes the year of a Japanese era is used instead of a year according to the Gregorian calendar. For example, the Heisei 平成 era began in 1989 and lasted until 2019, therefore:

• heisei juu-ni-nen
  平成１２年
  Twelfth year of the Heisei era.
  Year 2000. 2000 A.D. 2000 C.E.

This means 平成１２年１２月３１日 and ２０００年１２月３１日 refer to the same date.

The Gregorian year is based on the year of Jesus Christ's birth, A.D. meaning "anno domini" (in the year of our loud), and B.C. for negative year numbers meaning "before Christ." Japanese years are somewhat based on imperial eras, with some of them end with the death of an emperor. Nowadays, the Gregorian calendar is used globally, including by countries that don't consider Christ their lord, so the acronyms C.E. and B.C.E. are sometimes used instead for "common era" and "before common era."

The terms wareki 和暦 and seireki 西暦 refer to Japanese and Western calendars, respectively.

The word gan'nen 元年, literally "origin year," refers to the first year (１年) of an era and may be used as part of a date.

• 平成元年１２月３１日 and １９８９年１２月３１日 refer to the same date.

Eras may begin and end in the middle of years. The last year of Heisei is the 31st, and then Reiwa 令和 begins, but the Reiwa era only begins in 1st of May of 2019. From January to April of 2019, it's not Reiwa yet.^{(mynavi-agent.jp:履歴書の年号の書き方やルール)}

• heisei san-juu-ichi-nen shi-gatsu san-juu-nichi
  平成３１年４月３０日
  31st year of the Heisei era, month 4, day 30.
  30 of April, 2019.
• Reiwa gan'nen go-gatsu tsuitachi
  令和元年５月１日
  Origin year of the Reiwa era, month 5, day 1.
  1 of May, 2019.

The Japanese years were more common in the past before the globalization of Japan. They're still used, e.g. ceremonially and in documents, but nowadays Gregorian years are more common.

Naturally there was a generation of people who were born using Japanese years and had trouble adapting to such changes, doing stuff like:

• Saying dates, like their birth year, in Japanese years.
• Writing Japanese years when people expected Gregorian ones.
• Having trouble figuring out what year a Gregorian year is supposed to be.
• Having trouble converting one year to the other.

And so on. Could be some plot point in some manga or anime out there, like you have a character that looks young but is actually old as hinted, among other things, by their use of old-fashioned Japanese years or trouble reading Gregorian ones.

Anime: KADO: The Right Answer, Seikai suru Kado 正解するカド (Episode 1)

• Context: someone types a date.
• Heisei ni...
  平成２
  Heisei era, year 2...
• *backspace*
• ni-sen-juu-nana-nen shichi-gatsu ni-juu-go-nichi
  ２０１７年７月２５日
  25 of July of 2017. (also known as Heisei year 29).

Parentheses After Date

A kanji enclosed by parentheses after a date typically refers to the weekday that date falls in, e.g.:

• ２０００年０１月０１日（土）
  Year 2000, month 1, day 1, which is a doyoubi 土曜日, "Saturday."
• ２０００年０１月０２日（日）
  Year 2000, month 1, day 2, which is a nichiyoubi 日曜日, "Sunday."

So it's like writing (sat) for Saturday or (sun) for Sunday. It's an abbreviated way of writing the weekday.

nichi-youbi （日）曜日	Sunday.
getsu-youbi （月）曜日	Monday.
ka-youbi （火）曜日	Tuesday.
sui-youbi （水）曜日	Wednesday.
moku-youbi （木）曜日	Thursday.
kin-youbi （金）曜日	Friday.
do-youbi （土）曜日	Saturday.

For reference, an example:

Anime: Pop Team Epic, Poputepipikku ポプテピピック (Episode 4, Collage)

• Context: on the top-right corner, it reads: year 2014, month 11, day 28, a "Wednesday," suiyoubi 水曜日.
• Popuko "Kabedon shitee ❤"
  ポプ子 「カベドンしてェ❤」
  Popuko: "do a kabedon [on me] ❤"

X's, Circles, and Triangles in Dates

Sometimes you may see X marks, circle marks, and triangle marks in a date in Japanese, specially in manga and anime. These marks are placeholders used when a specific number isn't important or, in examples, where there are no specific numbers to begin with.

Manga: Uzaki-chan wa Asobitai! 宇崎ちゃんは遊びたい！ (Chapter 2, 後輩と映画館)

• Context: Uzaki-chan explains that sometimes someone wants to do something in a certain date (literally month "circle" day "X"), and that's not a date she's okay with, so she refuses (here shown crossing her arms in an X, a gesture of rejection).
  • ○月×日, i.e. month circle day X, could be any date. It's just there to say the other character said SOME date without specifying a specific date.

Anime: Inuyashiki いぬやしき (Episode 6)

• Context: a well-known murderer tells an anonymous bulletin board that he's gonna kill everyone in that thread.
• hon'nin desu ka? kao! up!!
  本人ですか？顔！うｐ！！
  Are [you] [the murderer himself]? [Your] face! Upload it!
  • hon'nin - the person themselves, as opposed to someone speaking in their behalf.
• nanashi-san atto oopun
  名無しさん＠おーぷん
  Anon @ open.
  • Open probably refers to open 2 channel, おーぷん2ちゃんねる, a bulletin board based on 2ch (2channel).
  • The incrementing numbers 193, 194, 195, 197, 197, and so on at the left side of each response is the identifier used to cite what a previous user posted.
  • The 2017/11/×× is the date. Note that the day is unspecified, with with two x's written instead.
• koroshite-miru baaaaaaaaaakka
  殺してみるバァーーーーーーーーッカ
  Try killing [me], stuuuuuuuuuuuuuuuupid.
• wwwwwwwwwwwwwwwwwwwwww
  ｗｗｗｗｗｗｗｗｗｗｗｗｗｗｗｗｗｗｗｗｗｗ
  *laughs anonymously.*
• keisatsu koko miteruu?
  警察ここ見てるー？
  Police, are [you] seeing [this]?
  • koko ここ, "here," as in "this thread."
  • miteru - contraction of mite-iru 見ている.
• oi kora, satsujinki, hayo jishu shiro
  おいコラ　殺人鬼　はよ自首しろ
  Hey, murderer, go surrender yourself already.
  • hayo - synonymous with hayaku 早く, "quickly."
• kuso-gaki ga
  クソガキが
  [You brat].
• nichan'neru shuuryouuu wwwwwwwwwww
  にちゃんねる　終了ーーｗｗｗｗｗｗｗｗｗｗｗ
  2channel is finisheeed, lolololololololololol.

Vocabulary

For reference, some relevant words:

• hidsuke
  日付
  The date on the calendar.
• nengappi
  年月日
  A date.
  Year, month, day.
  • seinengappi
    生年月日
    Birth date.
• nengatsu
  年月
  Years and months. (as in the passing of time.)
  Year and month. (as in a partial date without specific day)
  • toshi-tsuki
    年月
    Years and months. (passing of time only.)
• gappi
  月日
  Month and day. (date only.)
  
  • tsuki-hi
    月日
    Months and days. (passing of time only.)
    The Moon and the Sun.
• tsuki
  月
  The Moon.
  • See also: moon phases.
• hi
  日
  The Sun.
  A day.
  • haha no hi
    母の日
    Mother's day.
• kinenbi
  記念日
  Commemorative day. A day in which you celebrate something, e.g. an anniversary of something.
  • kinen-shashin
    記念写真
    Commemorative photo. A photo taken to record some occassion.
    • See also: peace sign.

How to Say the Words for Years, Months, and Days

It's possible to use the counters for years, months, and days to refer to just the year, month, or day alone, without any other part of the date.

• ni-sen-nen
  ２０００年
  The year two thousand.
• juu-ni-gatsu
  １２月
  Month 12.
  December.
• san-juu-ichi-nichi
  ３１日
  Day 31 of some month.

The words for months in Japanese are all pretty straightforward: just a number (specifically the on'yomi 音読み reading of the kanji, e.g. ichi, ni, san...) plus the ~gatsu morpheme. Beware the 9th month is read ku-gatsu, not kyuu-gatsu.^{(coelang.tufs.ac.jp)}

Month Name	In Japanese	romaji
January	一月いちがつ or １月	ichigatsu
February	二月にがつ or ２月	nigatsu
March	三月さんがつ or ３月	sangatsu
April	四月しがつ or ４月	shigatsu
May	五月ごがつ or ５月	gogatsu
June	六月ろくがつ or ６月	rokugatsu
July	七月しちがつ or ７月	shichigatsu
August	八月はちがつ or ８月	hachigatu
September	九月くがつ or ９月	kugatsu
October	十月じゅうがつ or １０月	juugatsu
November	十一月じゅういちがつ or １１月	juuichigatsu
December	十二月じゅうにがつ or １２月	juunigatsu

For years, too, pretty straightforward, just beware that "year one thousand" is sen-nen 千年, not issen-nen 一千年, this includes when talking about 1999, 1998, etc. Similarly, "year one hundred" is hyaku-nen 百年, not ippyaku-nen 一百年.

The words for days are complicated. The first day of the month has its own word: tsuitachi 朔日 (normally spelled １日). Days 2 to 10 are said using the kun'yomi 訓読み reading (hito~, fu~, mi~) together with a ~ka ～日 suffix. Days 11 and up use MOSTLY the on'yomi with ~nichi ～日. Days 14 and 24 use a mix of on-kun ending in the kun reading ~yokka ～４日, probably because if it was the on reading shi-nichi ４日 it would sound too similar to shichi-nichi ７日. Day 20 has its own reading: hatsuka. Incidentally, 10, 20, and 30 are supposed to be tooka, hatsuka, and misoka, respectively, but for some reason people don't use misoka. Finally, days 19 and 29 are read ending in ~ku-nichi ～９日, not ~kyuu-nichi. For reference, a table:^{(coelang.tufs.ac.jp)}

tsuitachi １日ついたち	juu-ichi-nichi １１じゅういち日	ni-juu-ichi-nichi ２１にじゅういち日
futsuka ２ふつ日	juu-ni-nichi １２じゅうに日	ni-juu-ni-nichi ２２にじゅうに日
mikka ３みっ日	juu-san-nichi １３じゅうさん日	ni-juu-san-nichi ２３にじゅうさん日
yokka ４よっ日	juu-yokka １４日じゅうよっか	ni-juu-yokka ２４日にじゅうよっか
itsuka ５いつ日	juu-go-nichi １５じゅうご日	ni-juu-go-nichi ２５にじゅうご日
muika ６むい日	juu-roku-nichi １６じゅうろく日	ni-juu-roku-nichi ２６にじゅうろく日
nanoka ７なの日	juu-shichi-nichi １７じゅうしち日	ni-juu-shichi-nichi ２７にじゅうしち日
youka ８よう日	juu-hachi-nichi １８じゅうはち日	ni-juu-hachi-nichi ２８にじゅうはち日
kokonoka ９ここの日	juu-ku-nichi １９じゅうく日	ni-juu-ku-nichi ２９にじゅうく日
tooka １０とお日	hatsuka ２０日はつか	san-juu-nichi ３０さんじゅう日
		san-juu-ichi-nichi ３１さんじゅういち日

Beware of some words related to dates that aren't about the date on the calendar, e.g.:

• shonichi
  初日
  First day.
  • Not the first day of the month, the first day of something.
  • gakkou shonichi
    学校初日
    The first day of school.
• saishuubi
  最終日
  Last day.

Also:

• shougatsu
  正月
  New year.
  • Although this ends in ~gatsu, it typically refers to the first three days of a new year.

Interrogatives

It's possible to ask a question about a date by combining the counters for date parts with nani 何, just as you could with any other counter.

• kyou wa nan-gatsu nan-nichi?
  今日は何月何日？
  Today is what-month, what-day?
  What's today's date?
  • A normal way to ask the day.
• sore wa nan-nen, nan-gatsu, nan-nichi?
  それは何年、何月、何日？
  That's what-year, what-month, what-day?
  What year, month, and day [did that happen]?
  • A phrase generally used in comedic effect to ask about an event in ridiculous detail.

Alternatively:

• sore wa itsu?
  それはいつ？
  When is that?

These interrogatives can combine with the ka か particle and the mo も particle:

• nan-nen ka wasureta
  何年か忘れた
  [I] forgot what year [it was].
• nan-nen mo mae
  何年も前
  An amount (no idea exactly, but lots) of years ago.
  Many years ago.

Date Ranges

It's possible to refer to a date range using the particles "from," kara から, and "until," made まで.

• ni-gatsu kara roku-gatsu made
  ２月から６月まで
  From month two until month six.
  From February to June.

Note that to express lengths of time, it varies:

• mikka-kan
  ３日間
  A span of time of three days.
• yokkagetsu
  ４ヶ月 (or ４箇月)
  Four months.
  • ~getsu, not ~gatsu.
• ni-nen-kan
  ２年間
  A span of time of a two years.
• isshou
  一生
  One's entire life. (has nothing to do with dates.)
• eien ni
  永遠に
  Eternally. (also has nothing to do with dates.)

Cyclic Dates

To say "every" year, month, or day, the prefix mai~ 毎～ is used, forming the following words:

• mai-nichi
  毎日
  Every day.
  • mai-asa
    毎朝
    Every morning.
  • mai-ban
    毎晩
    Every night.
• mai-shuu
  毎週
  Every week.
  • mai-shuumatsu
    毎週末
    Every weekend.
• mai-tsuki
  毎月
  Every month.
  • mai-tsuki dai-ni doyoubi
    毎月第２土曜日
    Every month, the second Saturday.
    The second Saturday of every month.
• mai-toshi
  毎年
  Every year.

To say "every N" days, months, or years, the suffix ~goto ～毎 is used. The phrase ~oki ni ～おきに has a similar meaning, too.

• futsuka-goto
  ２日毎
  Every two days.
• mikka-oki ni
  ３日おきに
  Putting three days between.
  Every four days.

For "every N days X things," the ni に particle is used with a length of time, essentially forming a temporal adverb. The rest of the sentence can be pretty much anything.

• ichi-nichi ni ikkai
  一日に一回
  One time every one day.
  Once per day.
  
  • ikkai
    一回
    Once.
• nikagetsu ni hon wo san-satsu yomu
  二ヶ月に本を３冊読む
  To read three books every two months.
  • hon wo san-satsu yomu
    本を３冊読む
    To read three books.

～号

Magazines published weekly or monthly may be referred by their issue "number," ~gou ～号, right after the year, which looks like a date, but isn't really.

• Shuukan Shounen Janpu
  sen-kyuu-hyaku-kyuu-juu-kyuu-nen
  yon-juu-san-gou
  週刊少年ジャンプ１９９９年４３号
  Weekly Shounen Jump, year 1999, issue 43.
  • Since this is a weekly magazine, there are up as many issues in a year as there would be weeks in a year (52 weeks, 52 issues).
  • Incidentally, this is the issue in which Naruto ナルト was first serialized.

Commemorative Dates Based on Wordplay

There is a form of wordplay involving dates in Japanese in which a month and day is said to commemorate something if the numbers spell a word (also known as goroawase 語呂合わせ).

For reference, some examples:^{(mostly from ffortune.net:語呂合わせの日)}

Date	Commemoration	Translation Note
毎月１２日 12th of every month	toufu no hi 豆腐の日 Tofu's day.	too １０, futatsu ２つ.
毎月１５日 15th of every month	ichigo no hi 苺の日 Strawberry's day.	ichi １, go ５.
毎月２２日 22nd of every month	fuufu no hi 夫婦の日 Husband & Wife's Day	futatsu ２つ, twice.
毎月２６日 26th of every month	furo no hi 風呂の日 Bath's day.	futatsu ２つ, roku ６.
毎月２８日 28th of every month	niwatori no hi 鶏の日 Chicken's Day.	ni ２, hachi ８. Historically, ha は and wa わ have similar pronunciations.
毎月２９日 29th of every month	niku no hi 肉の日 Meat's Day.	ni ２, ku ９.
１月５日 1st of January	igo no hi 囲碁の日 Go's Day.	ichi １, go ５. As in the board game Go.
	ichigo no hi 苺の日 Strawberry's Day.	ichi １, go ５.
２月９日 9th of February	fugu no hi 河豚の日 Puffer Fish's Day.	futatsu ２つ, ku ９. ku く with diacritic becomes gu ぐ.
	niku no hi 肉の日 Meat's Day.	ni ２, ku ９.
２月１０日 10th of February	niito no hi ニートの日 NEET's Day.	ni ２, too １０.
	futon no hi 布団の日 Blanket's Day.	futatsu ２つ, too １０.
２月２２日 22nd of February	neko no hi 猫の日 Cat's Day.	ni, ni, ni ２２２, because nya, nya, nya ニャニャニャ, "meow, meow, meow."
３月５日 5th of March	sango no hi 珊瑚の日 Coral's Day.	san ３, go ５.
３月８日 8th of March	mitsubachi no hi 蜜蜂の日 Honeybee's Day.	mittsu ３つ, hachi ８.
３月９日 9th of March	arigatou no hi ありがとうの日 Thank You's Day. Gratitude Day.	san ３, kyuu ９. sankyuu サンキュー katakanization of "thank you."
３月１３日 13th of March	sandoicchi no hi サンドイッチの日 Sandwich's Day. sandoicchi dee サンドイッチデー (same meaning.)	san, ichi, san ３１３, so ichi wo san de sando １を３でサンド(nansuka.jp) To sandwich 1 with 3's.
３月２７日 27th of March	sakura no hi 桜の日 Sakura's Day.	3 times 9 is 27. san ３, ku ９. sakura is a flower tree, the "cherry blossom," which blooms around this date, at the end of March.(i879.com)
４月６日 6th of April	shiro no hi 城の日 Castle's Day.	shi ４, roku ６.
５月１０日 5th of May	meido no hi メイドの日 Maid's Day	mei メイ, "May," plus do ど form too とお, "10." Maid in the sense of moe anime.(dic.nicovideo.jp)
５月２９日 29th of May	kon'nyaku no hi こんにゃくの日 Konjac's Day.	kokonotsu ９つ, ni ２, ku ９. Konjac is a food, a plant like potato.
６月４日 4th of June	mushi no hi 虫の日 Bug's Day. Insect's Day.	muttsu ６つ, shi ４.
	mushiba yobou dee 虫歯予防デー Dental Caries Prevention Day.
６月１６日 16th of June	mujuuryoku no hi 無重力の日 Zero-Gravity Day.	muttsu ６つ, juuroku １６.
６月２６日 26th of June	rotenburo no hi 露天風呂の日 Open-Air Bath Day.	6.26: roku, ten, futatsu, roku ten 点 being "dot."
７月３日 3rd of July	nami no hi 波の日 Wave's Day. saafaa dee サーファーデー Surfer's Day.	nana ７, mittsu３つ.
７月２５日 25th of July	kakigoori no hi かき氷の日 Shave Ice's Day.	nana ７, tsuu ２, go ５ natsu-goori 夏氷, "Summer Ice," another name for kakigoori, a sort of ice dessert.
７月２７日 27th of July	suika no hi スイカの日 Watermelon Day.	tsuu ２, nana ７. tsuna-moyou 綱模様, "rope pattern," which is found in watermelons, which are eaten in Summer, which is around this date.
８月１日 1st of August	maajan no hi 麻雀の日 Mahjong's Day.	hachi ８, ichi １ hai はい becomes pai ぱい pai 牌, "tile," with mahjong being a game played using tiles.
８月２日 2nd of August	pantsu no hi パンツの日 Pants' Day.	hachi ８, tsuu ２. ha は becomes pa ぱ.
８月３日 3rd of August	hachimitsu no hi 蜂蜜の日 Honey's Day.	hachi ８, mittsu ３つ
	hasami no hi ハサミの日 Scissor's Day
８月７日 7th of August	hana no hi 花の日 Flower's Day.	hachi ８, nana ７.
	hana no hi 鼻の日 Nose's Day.
	banana no hi バナナの日 Banana's Day.	Same as above, ha は becomes ba ば.
８月８日 8th of August	warai no hi 笑いの日 Laugh's Day.	hachi ８, hachi ８ ha'ha' ハッハッ, a laugh.
８月２９日 29th of August	yakiniku no hi 焼き肉の日 Fried Chicken Day. Fried "Meat" Day.	yattsu ８つ, ni ２, ku ９.
９月３日 3rd of September	kusa-yakyuu no hi 草野球の日 Grass Baseball Day.	ku ９, san３. Grass here refers to a grass lot where amateur baseball players go play.
１０月２日 2nd of October	toufu no hi 豆腐の日 Tofu's Day	too １０, futatsu ２つ.
１０月３日 3rd of October	tozan no hi 登山の日 Mountain-Climbing Day.	too １０, san ３. sa さ becomes za ざ.
１０月４日 4th of October	iwashi no hi いわしの日 Pilchard's Day. Sardine's Day.	ichi １, wa ０, shi ４. wa 輪, "ring," 0's shape.
１０月第１土 First Saturday of October	tsuchi no hi 土の日 Soil's Day.	juu 十, ichi 一 together form tsuchi 土.
１０月８日 8th of October	ki no hi 木の日 Tree's Day.	juu 十, hachi 八 together form 木.
１０月２０日 20th of October	risaikuru no hi リサイクルの日 Recycle's Day. Recycling Day.	From zero's shape: hitomawari-futamawari ひと回りふた回り 1 lap, 2 laps, likely in the sense of going around once, twice, over and over again.
１１月１日 1st of November	inu no hi 犬の日 Dog's Day.	wan, wan, wan １１１ "woof, woof, woof."
１１月１１日 11th of November.	sakkaa no hi サーカーの日 Soccer's Day.	11 vs. 11, because each team has 11 players in soccer.
１２月３日 3rd of December.	tejina no hi 手品の日 Magic Trick's Day.	One, two, three!

Why The Japanese Date Format is Best Date Format

The Japanese date format is surprisingly the best date format there is.

I say surprisingly because in general Japanese makes absolutely no sense and it's just a chaos of a language, but at least the dates it got right.

It only looks different from an American date format perspective because the American date formal is imperial units levels of wrong.

Allow me to explain: when writing a number, you want the order of the digits to be the most significant digit first and the least significant digit last.

For example, in 123, the digit 1 represents a bigger number than the digit 2 because it comes first. That 1 represents 100, while 2 only represents 20. And 3 is just 3. So if 1 changes, if the first digit changes, a LOT changes, but if 3 changes, if the last digit changes, then very little changes. Similarly:

Numerical value	Parts	Order of parts
2000-12-31	Year, month, date.	Biggest, big, small.
23:59:59	Hour, minute, second.	Biggest, big, small.
5' 10"	Feet, inches.	Big, small.

Now in some parts of the world dates are written with the insignificant, err, the least significant parts first, like 31st of December. Why does the day come first?

Well, probably because the month is less likely to change. You probably know what month it is right now, right? If you had an appointment within the next 5 days, that's probably going to be in the same month as this one, could be the next month, but most likely it's same month. Consequently, in practice, the part people care most about most of the time in a date is the day part, which is least significant numerically-speaking.

Then comes America and just has this nonsensical month-first date format. This makes no sense. It just doesn't. Who even came up with this thing?

In any case, making sense logically isn't just a feels-good kind of thing, it also has convenient consequences.

The year-month-day order is great because it can be easily sorted. If you have files in a computer, for example, or folders, directories, and their filenames start with a date, writing this date in a year-month-day order allows the dates to be sorted simply by sorting the files alphabetically.

• 2000-01-31-photo-of-a-cat.jpeg
• 2000-02-07-photo-of-a-dog.jpeg
• 2010-01-01-photo-of-a-big-cat.jpeg

This wouldn't with day-month-year: the 2010 file is sorted as the first one because it begins with day 01.

• 01-01-2010-photo-of-a-big-cat.jpeg
• 07-02-2000-photo-of-a-dog.jpeg
• 31-01-2000-photo-of-a-cat.jpeg

And it certainly wouldn't work with month-day-year.

• 01-01-2010-photo-of-a-big-cat.jpeg
• 01-31-2000-photo-of-a-cat.jpeg
• 02-07-2000-photo-of-a-dog.jpeg

Incidentally, the International Standards Organization also endorses this format due to reasons like the above. The ISO 8601 Standard, which refers to a standard way to write date and time internationally, is a year-month-day, then hour-minute-second.

References

• 履歴書の年号の書き方やルール、和暦・西暦の調べ方 - mynavi-agent.jp, accessed 2022-07-20.
• 語呂合わせの日 - ffortune.net, accessed 2022-07-20.
• 3月13日は『サンドイッチデー』って知ってた？ 由来とサンドイッチの豆知識をご紹介！ - nansuka.jp, accessed 2022-07-20.
• 桜の花言葉・歴史～3月27日はさくらの日～ - i879.com, accessed 2022-07-20.
• 日本語 文法 月・日付・曜日：カード - coelang.tufs.ac.jp, accessed 2022-07-21.
• メイドの日 - dic.nicovideo.jp, accessed 2022-07-25.