May
- Birthstone for May, August, September: Sapphire
- Birthstone for May, September: Agate
- Birthstones for January and May: Emerald
- Candy Lei
- Constitution Day, Norway
- Construction Flower Lei
- Dia de la Cruz
- Flower for May
- Lei Day
- Memorial Day
- Mother Goose Day
- National Dance Like A Chicken Day
- Poppy Pin
- Poppy Sponge Art
- Poppy-Shaped Sugar Cookies
- World Red Cross Day