What are the days of the week in kanji?

Sunday 日曜日 (にちようび), Monday 月曜日 (げつようび), Tuesday 火曜日 (かようび), Wednesday 水曜日 (すいようび), Thursday 木曜日 (もくようび), Friday 金曜日 (きんようび) and Saturday 土曜日 (どようび). Each name is one kanji (日月火水木金土) followed by 曜日 (ようび).

Why do the days of the week contain sun, moon, fire, water, wood, gold and earth?

The first kanji comes from the 七曜 (shichiyō), the seven luminaries: the Sun, the Moon and five planets. According to the National Astronomical Observatory of Japan (NAOJ), the planet names are tied to the five elements (五行): Mars is 火 (fire), Mercury is 水 (water), Jupiter is 木 (wood), Venus is 金 (metal, gold) and Saturn is 土 (earth).

How do you read the days of the week in Japanese?

The first kanji uses its on'yomi (Sino-Japanese reading): ニチ, ゲツ, カ, スイ, モク, キン, ド, followed by ヨウビ. So 火 is read か in 火曜日 (not ひ, as when it means fire on its own) and 月 is げつ (not つき).

Are the Japanese days of the week named after the planets?

Yes. NAOJ explains that the Japanese names follow the same seven luminaries as the Latin dies Solis, Lunae, Martis, Mercurii, Jovis, Veneris and Saturni, and the French lundi, mardi and so on. English and German replaced some of them with Germanic gods (Tuesday, Wednesday, Thursday, Friday), while Japanese kept the astronomical names.

When did the weekday names come to Japan?

They arrived in the Heian period with the 宿曜経 (Sukuyōkyō), brought by Kōbō Daishi (Kūkai), and were used on calendars for fortune-telling, not as a work week. A continuous weekday record appears in Fujiwara no Michinaga's 御堂関白記, from 998. Sunday became a day off for government offices on 1 April 1876 (Meiji 9), after the solar calendar was adopted in 1873.

Days of the Week in Kanji: 日月火水木金土 Explained

Short answer: the days of the week in Japanese are written 日曜日月曜日火曜日水曜日木曜日金曜日土曜日, read にちようび, げつようび, かようび, すいようび, もくようび, きんようび and どようび. Every name is one kanji, 日月火水木金土 (sun, moon, fire, water, wood, gold, earth), plus 曜日 (ようび), “day of the week”. The seven first kanji are the seven luminaries of the old calendar: the Sun, the Moon and five planets.

The origin of the names follows the National Astronomical Observatory of Japan’s calendar wiki, 曜日の名前 (国立天文台暦計算室), and the history of the weekday in Japan follows the National Diet Library Reference Collaboration Database. Readings are from the kanji data in Kanji Guide.

The seven days in kanji

Day	Kanji	Reading	First kanji	Luminary (per NAOJ)
Sunday	日曜日	にちようび	日 sun, day	Sun
Monday	月曜日	げつようび	月 moon, month	Moon
Tuesday	火曜日	かようび	火 fire	Mars
Wednesday	水曜日	すいようび	水 water	Mercury
Thursday	木曜日	もくようび	木 tree, wood	Jupiter
Friday	金曜日	きんようび	金 gold, metal	Venus
Saturday	土曜日	どようび	土 soil, earth	Saturn

All seven first kanji are JLPT N5. Each has a page with a picture story, example words and animated stroke order; the stroke rules are in the kanji stroke order guide.

Why every day ends in 曜日

The ending is 曜 (ヨウ, an N4 kanji with 11 strokes) plus 日 (び here). The Japanese Wiktionary describes 曜日 as a back-formation: people said 日曜日, 月曜日 and so on first, and 曜日 was then taken out of them as the word for “day of the week”.

You will also see short forms without the last 日: 日曜 (にちよう), 月曜 (げつよう) and so on, in speech and in writing.

Why sun, moon, fire, water, wood, gold, earth

The first kanji comes from the 七曜 (しちよう), the seven luminaries. According to NAOJ, the Sun and Moon are 日 and 月, and the five planets are named after the five elements (五行):

火 (fire): Mars
水 (water): Mercury
木 (wood): Jupiter
金 (metal, gold): Venus
土 (earth): Saturn

This is the same system behind the Latin names, dies Solis, Lunae, Martis, Mercurii, Jovis, Veneris and Saturni, and the French lundi, mardi, mercredi, jeudi and vendredi. English and German replaced some of the Roman gods with Germanic ones: Tuesday (Tiu/Ziu), Wednesday (Woden), Thursday (Thor) and Friday (Freya). Japanese kept the astronomical names, so its weekdays are the easiest to decode once you know the seven kanji.

How to read each first kanji

Each of these kanji has two kinds of readings (see onyomi vs kunyomi explained), and the weekdays use the on’yomi:

Kanji	On’yomi (used in the weekday)	Kun’yomi (stand-alone words)
日	ニチ (also ジツ)	ひ, か
月	ゲツ (also ガツ)	つき
火	カ	ひ
水	スイ	みず
木	モク (also ボク)	き
金	キン (also コン, ゴン)	かね
土	ド (also ト)	つち

So 火 reads か in 火曜日 but ひ when it means fire on its own, and 水 reads すい in 水曜日 but みず for water. To check a reading of any word, see kanji to hiragana.

Asking and saying the day

The question word is 何曜日 (なんようび), “which day of the week”. A simple question and answer:

今日は何曜日ですか。 (きょうはなんようびですか) “What day of the week is it today?”
今日は金曜日です。 (きょうはきんようびです) “Today is Friday.”

Days of the week on calendars

Japanese calendars often show only the first kanji in a row across the top: 日月火水木金土. If you know the seven kanji, you can read any calendar, timetable or opening-hours sign. They combine with dates and numbers, so it helps to know the Japanese numbers in kanji too.

When the weekday arrived in Japan

According to NAOJ, the seven-day names reached Japan in the Heian period with the 宿曜経 (Sukuyōkyō), brought by Kōbō Daishi (Kūkai). They were used on calendars for fortune-telling, not to organise a work week. The National Diet Library database gives the earliest continuous weekday notation as Fujiwara no Michinaga’s 御堂関白記, written in a 具注暦 from 998 (Chōtoku 4).

The weekday became part of daily life after the solar calendar was adopted in 1873 (Meiji 6). By a notice of the Dajōkan (no. 27, March 1876), from 1 April 1876 (Meiji 9) Sunday was a day off, and Saturday a half day, for government offices.

Practice the weekdays

The seven kanji are all JLPT N5, so they are among the first you meet. Try the N5 kanji quiz, browse the JLPT N5 kanji list, learn how to count days with Japanese counters, and if kanji as a whole is still new, start with what is kanji. Kanji Guide teaches every kanji with a picture story, readings and stroke order: open the study app in your browser or get the Kanji Guide iPhone app on the App Store.