noun
15th day of the 10th lunar month
A traditional date in the old lunar calendar, associated with the last of the three annual purification days (三元). Rare in modern usage outside historical or cultural contexts.
旧暦十月十五日は下元と呼ばれ、水官大帝を祀る日とされていた。
The 15th day of the 10th lunar month was called Kagen, a day for worshipping the Water Official Deity.
中元 is the 15th day of the 7th lunar month, the middle purification day; 下元 is the last of the three.
From Chinese tradition, combining 下 (lower/last) and 元 (origin/beginning), referring to the last of the three annual purification days (三元) in the lunar calendar.