Hemera was the goddess of day. She was listed among the first gods, the generations before the Titans and Olympians. Three different versions of her family tree exist in ancient writings. According to Hesiod's Theogony, the narrative detailing the genealogy of the gods, Hemera was the daughter of NYX (Night) and Erebos (Darkness), two primordial deities born from Chaos, the void or chasm before creation. The poet Bacchylides, on the other hand, named Nyx as Hemera's mother, but Chronos—the primordial god of time—as her father. Another version by Hyginus stated that Hemera emerged from CHAOS alongside Nyx, making her Hemera's sister, not mother.
Whether daughter or sister, Hemera was always closely linked with Nyx, their heavenly movements used to explain the cycle of day into night to the ancients. They moved in counterpoint to one another, Nyx retreating from the sky as Hemera appeared. Hesiod described them drawing near and passing one another, one entering a house while the other departed to pass over the earth, the house never holding them both inside.
In all ancient sources, Hemera was paired with Aether (Light), both her brother and consort. Sources differ, however, when it comes to their children. According to one version Hemera and Aether bore the Titans Gaia (Earth), Uranus (Sky) and Thalassa (Sea), while another version cited only Thalassa as the child of Hemera and Aether. Yet another claimed Uranus as their only child.
Given their similarities, some ancient texts closely associated Hemera with Eos, the goddess of the dawn. In some cases, the two goddesses were interchangeable. Philostratus the Elder uses their names interchangeably when describing a painting of the funeral of the Ethiopian king Memnon—also the son of Eos. In addition, both Callistratus and Pausanias, cited Hemera as Memnon's mother in their writings.