The night of the 十五夜 (Jugoya), known as the Harvest Moon or the Mid-Autumn Moon, falls on the 15th day of the eighth month in the old lunar calendar (October 6 in 2025). Its origins trace back to the “Mid-Autumn Festival” brought from China during the Heian period. In Japan, however, the timing coincides with the rice harvest season, so moon-viewing gradually became associated with giving thanks for the harvest and praying for abundance. Because taro is traditionally offered to the moon, this evening is also called the “Potato Moon” (芋名月). Steamed taro, moon-shaped dumplings, and pampas grass are set out as offerings—an image that continues to be cherished even today.
In contrast, the 十三夜 (Jusanya), or “Later Moon,” falls on the 13th day of the ninth lunar month (November 2 in 2025). Unlike the Jūgoya, this is a custom born in Japan, also during the Heian period, and it spread among the nobility as a companion to the Mid-Autumn celebration. The moon on this night is not perfectly full but slightly waning, and the Japanese of the time found beauty precisely in this “unfinished form.” They cherished the subtle, lingering beauty that contrasted with the perfect circle of the Harvest Moon—an appreciation that would later blossom into the aesthetics of wabi and sabi. Because chestnuts and beans are typically offered, this night is also affectionately called the “Chestnut Moon” (栗名月) or the “Bean Moon” (豆名月).
Tradition holds that celebrating only one of these occasions—either the 15th night or the 13th night—was considered inauspicious, a practice called “片月見 (katatsukimi),” or one-sided moon viewing. Yet today, many people have never even heard of the Jusanya, and most are content simply to enjoy the Harvest Moon. Personally, I prefer not to worry about superstition, but simply to admire the moon’s beauty as it is.
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