Doyo no Ushi
The Ox is one of the twelve signs of the Chinese zodiac, where each calendar day is associated with one Zodiac animal. Doyo no Ushi no Hi is the Day of the Ox in every Doyo period. It is customary in Japan to eat eels to prevent fatigue from hot summer weather on this day.
Doyo is the 18-day period before Shiritsu, the first day of each of the four seasons- Rikka (first day of summer), Risshu (first day of autumn), Ritto (first day of winter), Risshun (first day of spring). Every Doyo has a particular day called Doyo no Ushi no Hi, which is literally translated as the Day of the Ox (Ushi). The Ox is one of the twelve signs of the Chinese zodiac, which was introduced to Japan from ancient China. Each calendar day is associated with one of the Chinese Zodiac animals. The Day of the Ox is considered a special day in every Doyo period, and each region has events to celebrate it. Eating eel on Midsummer Doyo no Ushi no Hi is the most famous custom.
Ushi Yu (Ox Bath), taking hot or medicinal baths and swimming to fend off illness, is another custom associated with Doyo no Ushi no Hi. Ushi Yu comes from the practice of leading oxen to rivers and lakes to rejuvenate them.
The opinion that eels proivide good nourishment if you eat them originated in the Edo era. It is said that the custom of eating eel on Doyo no Ushi no Hi was started by the well-known scholar, Gennai Hiraga. Gennai advised an Unagi-ya (eel restaurant), to put up an advertisement saying “It’s Doyo no Ushi no Hi today”, taking advantage of the traditional belief that eating food with the sound U (oo) such as Uri (gourd) and Umeboshi (pickled plum) on Ushi no Hi combats fatigue during the hot summer. Business boomed, and the idea spread all over Edo.