Days of the week in Japanese: seven names in kanji, romaji and IPA

Seven luminaries: where the Japanese day names come from

Japanese names its days after the 七曜 shichiyō, the seven luminaries of Chinese astronomy: the Sun, the Moon and the five planets visible to the naked eye. Chinese had named those five planets after the five elements of its own cosmology, so Mars is 火星, the fire star, Mercury 水星, Jupiter 木星, Venus 金星 and Saturn 土星. Strip the word 星 (star) and add 曜日, and the planet becomes a weekday: Mars gives 火曜日, Venus gives 金曜日.

The system reached Japan early in the Heian period. Japanese Wikipedia's article on the days of the week traces it to the esoteric Buddhist text 宿曜経, brought back by monks who had studied in Tang China; the English Wikipedia article on the names of the days of the week credits the monk Kōbō Daishi with bringing the planetary names over. Court almanacs, the 具注暦, soon printed the day of the week beside each date, and the diary of the regent Fujiwara no Michinaga records it daily, which shows the week in use by 1007.

For most of the following thousand years the week served fortune-telling and little else. Calendars of the Edo period counted days within the lunar month, and nobody needed a weekday for that. The change came with the Meiji reforms: Japan switched to the Gregorian calendar in 1873, and in 1876 government offices adopted a weekly rest day on Sunday. From then on, 日曜日 was the day off and the seven names moved into daily life.

Kanji, hiragana and the one-character calendar forms

Printed text writes the days of the week in Japanese with kanji. Hiragana spellings such as げつようび appear in material for young children and learners, or as furigana, the small reading aids set above the characters. Romaji is a transcription for foreigners and is not how Japanese readers see the days.

Calendars, timetables and shop signs cut each name down to its first character: 月 火 水 木 金 土 日. A Japanese date in its long form puts that character in brackets after the day of the month, so 2026年10月28日(水) reads as Wednesday, 28 October 2026. The Unicode CLDR data that phones and computers use for Japanese defines exactly this pattern, year 年, month 月, day 日 and the bracketed weekday, and it prints 水曜日 in full only in the longest date format.

Speech drops the final 日 freely. 月曜 getsuyō and 金曜 kin'yō are everyday words for Monday and Friday; Wiktionary lists 月曜 as a synonym of 月曜日 and 何曜 as a shorter form of the question word 何曜日.

How to pronounce the Japanese weekdays

All seven days of the week in Japanese end in the same three syllables, yō-bi, with a long ō. Hold that vowel for two beats: よう is two kana and two units of length, written ː in the IPA, and a short yo-bi sounds clipped to Japanese ears.

The vowel u is weak in Japanese. It is unrounded, written [ɯ] or [ɨ] in the IPA column, and it is short and light, so the tsu of getsuyōbi passes quickly. Kin'yōbi keeps its n as a separate beat before the y: kin-yō-bi, never ki-nyō-bi. That is what the apostrophe in Hepburn romaji marks.

Japanese has a pitch accent where English has stress. Tokyo speech, as transcribed in Wiktionary after the NHK accent dictionary, starts getsuyōbi low, rises on the second syllable and falls after yō.

How to use the days of the week in Japanese sentences

To say on Monday, add the particle に: 月曜日に会いましょう, let's meet on Monday. In casual speech the に is often left out. Without any particle a weekday can also stand as the topic of a sentence with は: 土曜日は休みです, Saturday is a day off.

Habits take 毎週, every week, in front of the day: 毎週火曜日にジムに行きます, I go to the gym every Tuesday. Next and last are 来週 and 先週 placed before the day, so 来週の金曜日 is Friday next week and 先週の日曜日 last Sunday.

The question is 何曜日 nan'yōbi, which day of the week. Wiktionary gives the standard example 今日は何曜日ですか, what day is it today? The answer simply repeats the pattern: 今日は水曜日です.

Two words cover the rest of the week. 平日 heijitsu means weekdays, the working days, and 週末 shūmatsu, literally the end of the week, means the weekend. Both appear on opening-hours signs: 平日 9時から18時 means weekdays from 9:00 to 18:00.

Does the Japanese week start on Sunday or Monday?

Japanese calendars commonly open the week on 日曜日. The Unicode CLDR week data, which sets the default first column of calendars in software, lists Sunday as the first day for Japan, as it does for Korea and the United States. The international standard ISO 8601 numbers Monday as day 1, the order used in the table above.

Whichever column comes first, the names keep their sequence: Sun, Moon, fire, water, wood, metal, earth. It is the planetary order of the Roman week, so 火曜日 sits where English has Tuesday, the day of Mars, and 土曜日 where English has Saturday, the day of Saturn.

The days of the week in Korean are built from the same seven characters, read the Korean way: 월요일 for Monday, 일요일 for Sunday.