East Asian names for days of the week are very similar. The system parallels the Latin system, and follows the order of the so-called ‘Seven Luminares’. The sun, moon, and 5 (visible) planets were called in ancient Chinese the Seven Luminares – 七曜 (qī yào), similar to the ancient Greeks and Romans who called them the seven planets. 月曜日 stands for moon day, representing the moon, and 日曜日 stands for sun day, representing of course, the sun. You will notice that the Kanji for the other 5 days of the week have meanings of particular elements, and these elements equate to 5 planets. I’ll give the days of the week in Japanese first, the pronunciation and Kanji then continue.
Monday – getsuyoubi – 月曜日
Tuesday – Kayoubi – 火曜日
Wednesday – Suiyoubi – 水曜日
Thursday – Mokuyoubi – 木曜日
Friday – Kinyoubi – 金曜日
Saturday – Doyoubi – 土曜日
Sunday – Nichiyoubi – 日曜日
Tuesday – Fire – Mars.
Wednesday – Water – Mercury.
Thursday – Wood – Jupiter.
Friday – Gold/Metal – Venus.
Saturday – Earth – Saturn.
This came because of the ancient Chinese theory of the ‘5 elements’ – 五行 (wǔ-xíng). which was used to explain the universe. They equate to several other things as well as planets. Japan, China and Vietnam still call the 5 planets by ‘water star’, ‘fire star’ etc.
My Generation Japan 
Cool post! Chinese doesn’t actually use these days though. They number the days One to Six and then have “Sun day”.
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Ooh okay, i’ll have to update that. Thank you for letting me know!
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Your welcome. I think classically they probably did use the same system as the Japanese too. Have you looked into the classical names for the Japanese months? They are really interesting too!
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I haven’t looked into that actually no. I suppose I’d never suspected it would have been different to the current system. But you’ve interested me now so i’ll have to do some research 😀
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