Months of the Year in Japanese

Every guide to Japanese months tells you the same thing: it's easy, just put a number in front of 月. And that's true. January is 一月 — "month one." But that easy answer is hiding the actual story, which is that Japan used to have month names so beautiful they're still given to children — and then, in 1873, the government threw them all out.

Here's the easy part first, because you came for it. The 12 months are simply the numbers 1 to 12 plus 月 (gatsu, "month"):

一月 ichigatsu · 二月 nigatsu · 三月 sangatsu · 四月 shigatsu · 五月 gogatsu · 六月 rokugatsu · 七月 shichigatsu · 八月 hachigatsu · 九月 kugatsu · 十月 jūgatsu · 十一月 jūichigatsu · 十二月 jūnigatsu

Two traps even in the easy version. April is shigatsu, not yongatsu — it uses the older shi reading of four. July is shichigatsu, not nanagatsu. And September is kugatsu, never kyūgatsu. Japanese has two number systems and months pick from both — get one wrong and you've named a month that doesn't exist.

The names Japan deleted

Before 1873, Japan ran on a lunar calendar, and every month had a name — not a number, a name with a meaning. March was Yayoi (弥生), "the month of new life." May was Satsuki (皐月), the rice-planting month. November was Shimotsuki (霜月), "the frost month." December was Shiwasu (師走) — literally "priests run," because even Buddhist priests, normally the calmest people in any room, are rushing around with year-end rites.

Then in 1873 the Meiji government scrapped the lunar calendar overnight and adopted the Western Gregorian one. The poetic names didn't fit the new months cleanly, so they were quietly dropped in favour of plain numbers. Efficient. Modern. And a small, deliberate act of forgetting.

The month that argues with itself

June, Minazuki (水無月), is the one old name that linguists still can't agree on. Read the middle kanji 無 the obvious way and it means "nothing" — the "month without water," which makes no sense for what is, in modern Japan, the start of the rainy season. But classical Japanese also used 無 as a connective particle meaning "of." Under that reading it flips to "the month of water" — the month the rice paddies are deliberately flooded. A competing theory sidesteps the kanji entirely: in the old lunar calendar, Minazuki fell roughly in what is now July, after the rains had passed and the summer heat had dried the land out. One name, three explanations, no consensus.

Except they didn't fully disappear

Flip the calendar above to "Old lunar names" and you're looking at words a modern Japanese person still half-knows. Yayoi and Satsuki are common girls' names — parents are, without quite thinking about it, naming their daughters after March and May. Shiwasu still appears every December in news headlines and shop signage to evoke that specific end-of-year rush. The old names survive the way Latin survives in English: not spoken daily, but embedded, showing up in names, poetry, and set phrases.

The month the gods leave

The strangest old name is October: Kannazuki (神無月), "the month without gods." Japanese tradition holds that every October, all eight million Shinto deities leave their home shrines and travel to Izumo Taisha, one of the oldest shrines in the country, for a grand annual meeting.

So across most of Japan, October is the godless month. But in Izumo itself — where the gods are actually gathering — the very same month is called Kamiarizuki (神在月), "the month with gods." One month, two opposite names, depending on which side of the divine meeting you're standing on. No numbered calendar can do that.

Saying "in [month]"

The grammar is mercifully simple. To say something happens in a given month, add the particle に (ni) after it: 三月に (sangatsu ni) — "in March." No declensions, no gendered articles, no contractions. After the irregular number readings, Japanese gives you the easiest "in [month]" rule of any language on this site.

Sources

• Standard references on the Meiji calendar reform of 1873 (Meiji 5→6), when Japan adopted the Gregorian calendar
• The traditional lunar month names (旧暦の月の異名) and their meanings — widely documented in Japanese cultural and linguistic references
• Izumo Taisha's own tradition of Kamiarizuki versus the nationwide Kannazuki
• Minazuki (水無月) has competing etymologies. The kanji 無 is popularly read as "nothing" ("month without water"), but is classically interpreted as a connective particle meaning "of" ("month of water"), referring to flooding the rice paddies. A separate theory attributes the "waterless" sense to the old lunar calendar placing this month in what is now post-rainy-season July. Discussion of both readings: Kodawari Times, "Minazuki" (kodawari-times.net/tips/minazuki)

Related

• Numbers 1 to 10 in Japanese — the counting system the months are built from
• Days of the Week in Japanese — which kept their poetic names
• Months in Mandarin Chinese — the same numbered system, different history
• Months in Polish — the opposite extreme: every month named for nature
• Months in German
• Language & Culture Hub