Tod

ay is "
unagi うなぎ (fresh water eel) day" or in Japanese it's called "
doyou-no ushi-no hi 土用の丑の日" or midsummer day of the Ox. On this day, you may see many advertisements of eel products at supermarkets and convenience stores. Japanese restaurants may also add eel as one of their lunch menus to choose from.
Thi

s tradition had its origins in the Edo period 200 years ago. Before 1873, instead of the Gregorian calendar, the
Japanese calendar was used and is based on the
lunisolar calendar adapted from the Chinese. Each season has its doyou which last 18 days. During this 18 days, each day is represented by one of the twelve animals of the
Chinese zodiac. Hence, within the 18 days, for certain years, there could be more than 1 day of the

Ox. The midsummer or summer doyou is especially important to the Japanese where they would send presents and greeting cards to friends and relatives. Yet, an eel restaurant owner then, had poor business and consulted a Japanese scholar,
Hiraga Gennai who was also a pharmacologist and a multi-talented genius who invented m

any items. Gennai suggested the restaurant owner to put up an advertisement "doyou-no ushi-no hi" as the people would think of eating dishes that had the letter "u" on this Ox day (
ushi-no hi). It is funny that other food for instance, udon could face the same fate, but somehow unagi caught on with popularity since then. It was interesting that eel restaurant owners had a superstition carried through from the Edo period as well, that broiling eels on other days such as on a Rat or Tiger day, would not taste as good as broiling them on an Ox day.