Japan's day-of-the-week names derive from the seven luminaries.
Tips
culture
The 七曜 system entered East Asia from Babylonian/Hellenistic astronomy via India. Japanese weekday names still preserve it directly: 日曜日 (Sunday), 月曜日 (Monday), 火曜日 (Tuesday/Mars), 水曜日 (Wednesday/Mercury), etc.
history
First systematically introduced to China in the Tang dynasty through Buddhist astronomical texts like 七曜攘灾决. Influenced fortune-telling and the 七曜历 calendar.
