The beautiful thing about our religion is that not only do we have a clear way to honor the Theoi, and incentive to do so, we also get to live in a world governed completely by the Theoi. Hellenismos is special in that regards because it also largely matches up with science. To me--and many others with me--that is something very comforting. Now, as you are probably all aware, I live in a world full of Gods and Nymphs; for example, I take great strength in greeting Eos each morning as she paves the way for Helios, but there are many Gods who are, or who control, the cycle of day and night, and I would like to write out this cycle, if I may.

For all things geneological, I will always turn to Hesiod first. In his 'Theogony', he speaks of the birth of the Dawn, Sun and Moon:

"And Theia was subject in love to Hyperion and bare great Helios, and clear Selene, and Eos." [177]

Diodorus Siculus, in his 'Library of History' shares this world vieuw and moves a (pseudo-scientific) step beyond it:

"Of Hyperion we are told that he was the first to understand, by diligent attention and observation, the movement of both the sun and the moon and the other stars, and the seasons as well, in that they are caused by these bodies, and to make these facts known to others; and that for this reason he was called the father of these bodies, since he had begotten, so to speak, the speculation about them and their nature." [5.67.1]

Hyperion (Ὑπερίων), meaning 'The High-One', was a Titanes God born from Gaea and Ouranos. Theia and Euryphaessa (as mentioned in, for example, the Homeric Hymns) are generally regarded as the same Deathless woman: 'Theia' is the Hellenic word for 'Goddess', so it was likely 'Theia Euryphaessa' translated to 'Goddess Euryphaessa'. This means that the family tree is as follows:

     Khaos ------------ Gaea
         |         |
   Ouranos --- |
                       Hyperion --- Euryphaessa
                  Eos - Helios - Selene

The three of them--put into motion by Hyperion--form the basic cycle of these planets associated with specific times of day. Yet, the ancient Hellenes saw Night and Day as quite seperate from the heavenly bodies that are associated with them today. I have spoken before of the Protogenoi, and how They--contrary to the Olympians--are actually of the world; They, together, form the tapistry of earth and life. They literally make up our universe. As such, the further towards the Big Bang you go, the more abstract the Theoi become; They take on large, mostly unformed, chunks of the material that makes up our world and the further away you go from Khaos, the more specialized the Gods become--as well as numerous.

As such, starting this explination with Hyperion is actually incorrect--I should have started with Khaos itself, but if not there, than at least with Nyx, who is the deep Night, and Her daughter Hêmera (Ἡμερα), who is the Protogenos of the Day and the sister-wife of Aither (Light). In Hellenic mythology, Nyx draws a veil of darkness between the shining atmosphere of the aither and the lower air of earth (aer) at set times in the day, bringing night to man. In the morning, Hêmera removes this veil, and exposed the Earth once more to Light. As Hesiod writes in the Theogony:

"[At the ends of the earth, where lie the roots of earth, sea, Tartaros :] There stands the awful home of murky Nyx wrapped in dark clouds. In front of it [Atlas] the son of Iapetos stands immovably upholding the wide heaven upon his head and unwearying hands, where Nyx and Hemera draw near and greet one another as they pass the great threshold of bronze: and while the one is about to go down into the house, the other comes out at the door. And the house never holds them both within; but always one is without the house passing over the earth, while the other stays at home and waits until the time for her journeying come; and the one holds all-seeing light (phaos) for them on earth." [744]

Once we reach AD times, Hêmera is often identified with Eos, but in centuries prior, she was very much Her own Goddess, and Hêmera was as well. Hómēros, for example, in the 'Odysseia' writes: 

"The ship [of Odysseus] in due course left the waters of the river Okeanos and reached the waves of the spacious sea and the island of Aiaia; it is there [Okeanos] that Eos the early-comer (Erigeneia) has her dwelling place and her dancing grounds, and the sun himself has his risings. We came came in; we beached our vessel upon the sands and disembarked upon the sea-shore; there we fell fast asleep, awaiting ethereal Dawn." [12.1]

So, to recapitulate: Nyx and Hêmera continually work to both create and dissolve darkness on Earth; Selene moves with Nyx, and Helios with Hêmera, as heralded by Eos. In this recap, it is quite obvious we are yet missing a speciffic time of the day: dusk, or the evening. This was in the domain of the Nymphs, in this case the Hesperides (Ἑσπεριδες), who--depending of source--are either the daughters of Nyx or Atlas. Diodorus Siculus, in the 1st Century BC., wrote in his 'Library of History': 

"Now Hesperos (Evening) begat a daughter named Hesperis (Evening), who he gave in marriage to his brother [Atlas] and after whom the land was given the name Hesperitis; and Atlas begat by her seven daughters, who were named after their father Atlantides, and after their mother Hesperides." [4. 26. 2]

Yet, older sources agree that the Hesperides were born from Nyx; Hesiod, for example:

"And Nyx (Night) bare hateful Moros (Doom) and black Ker (Violent Death) and Thanatos (Death), and she bare Hypnos (Sleep) and the tribe of Oneiroi (Dreams). And again the goddess murky Nyx, though she lay with none, bare Momos (Blame) and painful Oizys (Misery), and the Hesperides who guard the rich, golden apples and the trees bearing fruit beyond glorious Okeanos."

Of course, there are more Gods--motly Titans--who are in some way connected to the cycle of night and day, but these are the most important ones and it's quite a hand full already. So perhaps next time when you awake, you will think of Hêmera, and rosy Eos, and when the sun is high in the sky, you will think of Him as well, and when you look upon the Moon before going to bed, you will give honors to Selene and Nyx, who holds Her and Gaea in Her embrace. Our Gods are everywhere; you only have to be aware of Them to notice.