This delicious Asian "show" flower, especially common on the east coast, has been planted throughout America. It gets its name because each flower lives only 1 day.
Use the shoots in early spring, and the flower buds, flowers, and wilted flowers in late spring and early summer.
Caution: Daylilies, especially the raw shoots, cause digestive distress in about 1 out of 50 people, and in rare circumstances (I've never seen this happen), the compounds that cause this are concentrated enough to make anyone sick.