Days & Months in Japanese
Japanese months are wonderfully logical -- just a number plus 月 (month). Days of the week follow a poetic pattern based on nature elements. But the days of the month are where it gets tricky: the first ten days have irregular readings rooted in ancient Japanese counting. This guide covers all three systems with the readings you need to know.
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Days of the Week
Japanese weekdays follow a beautiful pattern using natural elements: Moon, Fire, Water, Wood, Metal, Earth, and Sun. Each day ends with 曜日 (youbi, "day of the week").
In casual speech and writing, Japanese people often abbreviate days to just the element kanji: 月 (Mon), 火 (Tue), 水 (Wed), 木 (Thu), 金 (Fri), 土 (Sat), 日 (Sun). You will see this on calendars and schedules everywhere.
Months of the Year
Japanese months are the easiest part: simply combine a number (1-12) with 月 (gatsu, "month"). No separate month names to memorize.
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Days of the Month (The Tricky Part)
The first ten days of the month have irregular native Japanese readings that must be memorized. After the 10th, most days follow a regular pattern using Sino-Japanese numbers plus 日 (nichi).
After the 10th, days generally follow the regular pattern: 十一日 (juuichinichi, 11th), 十二日 (juuninichi, 12th), and so on. The exceptions are 十四日 (juuyokka, 14th), 二十日 (hatsuka, 20th), and 二十四日 (nijuuyokka, 24th).
The 20th of the month, 二十日 (hatsuka), is another important irregular reading. It comes from the same ancient counting system as the first ten days. This is a must-know for daily life in Japan.
Putting It Together
- 今日は何曜日ですか？ (Kyou wa nan youbi desu ka?) -- What day of the week is it?
- 今日は月曜日です。 (Kyou wa getsuyoubi desu.) -- Today is Monday.
- 誕生日は三月五日です。 (Tanjoubi wa sangatsu itsuka desu.) -- My birthday is March 5th.
Frequently Asked Questions
Why are the first ten days of the month irregular in Japanese?
The readings for days 1-10 come from the native Japanese (kun'yomi) counting system, which predates the Chinese-derived (on'yomi) numbers. These native readings (tsuitachi, futsuka, mikka, etc.) survived because dates were used in daily life long before the Chinese number system was adopted. After the 10th, most dates switch to the more regular Sino-Japanese readings.
How do months work in Japanese?
Japanese months are beautifully simple: just combine the number with 月 (gatsu, month). January is 一月 (ichigatsu, "month one"), February is 二月 (nigatsu, "month two"), and so on. No separate names to memorize -- if you know numbers 1-12, you know the months.
How do I say a full date in Japanese?
Japanese dates follow the pattern year + 年 + month + 月 + day + 日: 2026年3月5日 (nisen nijuuroku nen sangatsu itsuka) for March 5, 2026. Japan also uses the era system: 令和8年 (Reiwa 8 nen) for 2026.
What is the difference between ๆๆๆฅ and ไธๆ?
月曜日 (getsuyoubi) is Monday (the day of the week). 一月 (ichigatsu) is January (the month). Both contain 月 (moon/month) but in very different contexts. 曜日 (youbi) marks it as a day of the week, while the number before 月 marks it as a month.
Do Japanese people use the Western calendar?
Yes, Japan uses the Gregorian calendar (西暦, seireki) for most purposes. However, official documents, government forms, and some traditional contexts also use the Japanese era system (和暦, wareki). The current era is 令和 (Reiwa), which started in 2019.