Genethlion referred to birthday festivals celebrating the births of gods, heroes, or important mortals, deriving from genesis (birth). Communities honored deities on their traditional birth dates with sacrifices, hymns, and festivities. These celebrations acknowledged divine entry into the world and sought continued favor. In poetry, Genethlion symbolizes nativity, divine incarnation, and cyclical celebration of sacred origins, appearing in works exploring theogony, the marking of time through divine biography, birthday customs, and the Greek practice of maintaining calendrical connections to mythological events through annual commemorations linking human temporal experience with divine timelessness.

Genethlion celebrates divine or heroic births, particularly Apollo's birth on Delos. The festival illustrates Greek practices of commemorating mythological birthdays and the religious significance of nativity celebrations. Understanding Genethlion helps contextualize birthday celebrations in Greek culture and their evolution from religious to more personal observances. The emphasis on divine births demonstrates Greek interests in the circumstances of divine nativity and their ritual commemoration.