HEMERA was the Protogenos (primeval goddess) of the day. She was a daughter of Erebos (Darkness) and Nyx (Night) and the sister-wife of Aither (Light).

In the evening Hemera's mother Nyx drew a veil of darkness between the shining atmosphere of the aither and the lower air of earth (aer) bringing night to man. With each morn Hemera dispersed night's mists, bathing the earth again in the shining light of heaven (aither). In the ancient cosmogonies night and day were substances distinct and quite independent from the sun.

Hemera was closely identified with Hera, the queen of heaven, and Eos, goddess of the dawn. Hesiod appears to regard her as more of a divine substance rather than anthropomorphic goddess. She was largely irrelevant in mythology, with her role being wholly subsumed by the goddess Eos.