Days of the Week in Japanese

The days of the week are among the first words to learn in Japanese. Their logic is simple: all share the same suffix, and only the first kanji changes from one day to another. Understanding this structure, and the origin of each kanji, makes memorization quick and lasting.

The table of the 7 days of the week

Each day is built on the same model: a kanji representing a celestial body or an element, followed by 曜日 (yōbi). The suffix 曜日 is invariable. Only the first character changes.

The suffix 曜日 is composed of two kanji. The first, 曜 (yō), is used only to designate the days of the week — it is not used in other contexts. The second, 日 (bi here, but also nichi or hi depending on the word), means “sun” or “day”. Together, they form the word 曜日 which means “day of the week”.

In Japanese, kanji readings follow two systems: the on reading (of Chinese origin) and the kun reading (of Japanese origin). In the names of the days, the first two kanji (the element + 曜) are read as on, while the last kanji 日 is read as kun: it becomes –bi due to rendaku (voicing). For example, in 月曜日: getsu (on) + yō (on) + bi (kun).

The origin of the names: the five elements and the seven celestial bodies

The names of the Japanese days come from Chinese astronomy and philosophy, transmitted to Japan over the centuries. Understanding this origin facilitates memorization and reveals a worldview common to several cultures.

In Chinese Taoist thought, the cosmos is governed by the Sun, the Moon, and five planets visible to the naked eye. These seven celestial bodies form the 七曜 (shichiyō), literally “the seven luminaries”. Each planet is associated with one of the five fundamental elements of Chinese cosmology, the 五行 (gogyō):

This system is not unique to Japan: the Romans used the same order of planets, inherited from the Greeks. This is why the names of the days in French and Japanese correspond exactly to the same celestial bodies. Monday comes from “Luna” (the Moon), just as 月曜日 comes from 月 (moon). Tuesday comes from “Mars”, just as 火曜日 comes from 火 (fire, the Japanese name for the planet Mars). The correspondence is identical from Monday to Friday. Only Saturday and Sunday diverged in French under the influence of Christianity (Sabbath and “Lord’s Day”), while Japanese retained Saturn and the Sun.

This order of the seven celestial bodies arrived in Japan via China, probably brought by the Buddhist monk Kūkai (空海, also known as Kōbō Daishi) upon his return from his journey to China in the 9th century. For several centuries, this system remained confined to astrology. It was only with the adoption of the Gregorian calendar in 1873, during the Meiji era, that the seven days named after celestial bodies became official in Japan.

The details of each day

Knowing the meaning of the head kanji for each day helps to memorize them without brute repetition effort.

月曜日 (getsuyōbi) — Monday. The kanji 月 means “moon” and, by extension, “month”. It is the same character used in 今月 (kongetsu, this month) or 来月 (raigetsu, next month). The reading getsu comes from Chinese, but 月 is also read tsuki in other contexts (the moon in the sky).

火曜日 (kayōbi) — Tuesday. The kanji 火 means “fire”. It is the Japanese name for the planet Mars, whose red color evokes flames. It is found in words like 火山 (kazan, volcano) or 花火 (hanabi, fireworks).

水曜日 (suiyōbi) — Wednesday. The kanji 水 means “water”. It is the Japanese name for Mercury. It is found in 水泳 (suiei, swimming) or 水族館 (suizokukan, aquarium).

木曜日 (mokuyōbi) — Thursday. The kanji 木 means “tree” or “wood”. It is the Japanese name for Jupiter. It is found in 木材 (mokuzai, construction wood) or 木の葉 (ki no ha, tree leaf).

金曜日 (kinyōbi) — Friday. The kanji 金 means “gold” or “metal”. It is the Japanese name for Venus. It is found in 金魚 (kingyo, goldfish) or お金 (okane, money). Friday is often associated with good mood in current Japanese culture, just like in the West.

土曜日 (doyōbi) — Saturday. The kanji 土 means “earth” or “soil”. It is the Japanese name for Saturn. It is found in 土地 (tochi, land) or 泥土 (deido, mud).

日曜日 (nichiyōbi) — Sunday. The kanji 日 means “sun” or “day”. It is the first day of the week on Japanese calendars. This same kanji appears in 今日 (kyō, today) and in 日本 (Nihon/Nippon, Japan — literally “origin of the sun”).

The week starts on Sunday in Japan

On Japanese calendars, the week begins on Sunday (日曜日) and ends on Saturday (土曜日). This organization differs from the French calendar which starts on Monday. It comes from the influence of the original astronomical system: the Sun, the first of the seven celestial bodies, naturally opens the cycle.

This difference has practical importance: reading a Japanese diary, schedule, or application requires adjusting one’s bearings. Sunday is therefore found in the first column on the left, where the French place Monday.

The working week, however, remains the same: Monday to Friday. Weekdays are called 平日 (heijitsu, literally “ordinary days”). The weekend is called 週末 (shūmatsu, literally “end of week”).

Abbreviated forms of the days

Japanese has several levels of abbreviation for the days of the week. Depending on the context, the short or very short form is used instead of the full form.

The short form (without the final –bi) is used in written texts and conversations where the context is clear. The single kanji appears on schedule boards in transportation, shop signs, and printed calendars. For example, on a restaurant window, one might read: 月・水・金 to indicate that the establishment is open on Monday, Wednesday, and Friday.

Using days in sentences

The days of the week are used with the particle に (ni) to indicate that an event happens on that day. This particle is placed directly after the name of the day.

To ask what day it is, the formula is:

The interrogative word 何曜日 (nan’yōbi) means “what day of the week”. Note: it is pronounced nan’yōbi and not na-nyōbi — the apostrophe marks the pause between n and y.

To place a day in the current, next, or past week, here are the useful expressions:

Planet names: a vocabulary bonus

Knowing the days of the week directly opens access to the names of the planets in the solar system in Japanese. The principle is identical: the kanji 星 (sei, “star, planet”) is added to the kanji of the element.

Planets discovered after antiquity (Uranus, Neptune) received different Japanese names, as they were not known when this system was created. Uranus is called 天王星 (tennōsei) and Neptune is called 海王星 (kaiōsei).

Practical exercise

Test your knowledge of the days of the week in Japanese: