She was the daughter of Chaos and Caligo (Mist), and the counterpart of the Greek goddess Hemera.

According to the Roman mythographer Hyginus, Chaos and Caligo were the parents of Nox (Night), Dies, Erebus (Darkness), and Aether.

[3] While, Hyginus says that, in addition to Caelus, Aether and Dies were also the parents of Terra (Earth), and Mare (Sea).

[4] Cicero also says that Dies and Caelus were the parents of Mercury, the Roman counterpart of Hermes.

[5] The Latin noun diēs is based on the Proto-Italic accusative singular *dijēm, itself stemming from the Proto-Indo-European root *dyeu-, denoting the "diurnal sky" or the "brightness of the day" (in contrast to the darkness of the night).