5/29 - May twenty-nineth Konjaku Day (Konnyaku no hi)
Konjaku, also known as devil's tongue, is a plant. But when the work konjaku used in Japan, it mostly means the food made by the plant. 5 sounds similar to "Ko", 2 sounds similar to "Nya" and 9 "ku" in Japanese. So the day is named Konnyaku no hi.