Hemera or Heméra (Greek: Ἡμέρα, "Day") or Amara (Αμαρα, "Day"), in Greek myth, was the daughter of Nix (the night) with Erebo (darkness), a primordial entity and the personification of daylight and the morning cycle.
According to the Roman poet Hyginus, she had a romance with her brother Aether and with him had three children, Gaia (the Earth), Uranus (Latin: Coelus, the sky), and Thalassa (the sea). She was born together with Aether and the Hesperides. Hemera's equivalent in Roman myth was Dies.
Some traditions place Aether and Hemera as the parents only of Uranus and Gaia, consequently as the "grandparents" of almost all the Greek gods. According to mythology, moments before Hemera conceived Uranus and Gaia, great thunders were heard throughout the universe, as if the sky was being influenced by the goddess (it is said that this is because Hemera had a strong bond with Ether).
After the titanomachy, Hemera became part of the retinue of Helios, god of the sun, along with the Hesperides. She was also the guardian of the thresholds and of the portals between the world of light and the world of darkness.
According to Hesiod, Hemera lives with her mother, Nix, beyond the Ocean, in the far west. There, a great wall separates the gates of hell from the visible world. Behind the wall stands an imposing great palace where both reside, but are never seen together.
When Hemera leaves, the mother waits until her daughter's time to return to greet her in turn, and leaves to cast the cloak of night over the world. When Nix returns to the palace, he greets his daughter and gives her permission to go out with Helios and the Hesperides to illuminate the earth until evening, and the cycle begins again. As Hesiod says, "never does the palace close with both."
Hemera has great beauty, not as great as Aphrodite's, but enough to also be considered a goddess of persuasion and lies, who through cunning can manipulate both mortals and the other gods with a certain ease. She has also always been associated with the god Apollo, and they could even have a relationship as "brothers in heart", since Apollo is considered a morning sun deity.
In the book The House of Hades, from the Heroes of Olympus saga written by Rick Riordan, Hemera is mentioned as a daughter by Nix.