Years of the Trees
The centuries before the Sun and Moon.
The long years that lay between the founding of Valinor and its Darkening. During this time, Valinor was lit by the light of the Two Trees, but Middle-earth lay in darkness.
Long before the Elves awoke, Yavanna created the Two Trees of Valinor to give light to realm of the Valar. So began a reign of peace in Valinor, but Middle-earth was lit by starlight alone, and Melkor worked in the depths of Utumno in the north of the World. We are not told how long this time lasted, just that 'the ages drew on', so this period must have been at least 6,000 years, and probably longer. It was during this period that AulÃ« made the Dwarves, and set them to sleep until the coming of the Elves.
When OromÃ« discovered that the Elves had awoken at CuiviÃ©nen, great changes came about. The Valar made war on Melkor to protect the Elder Children of IlÃºvatar; Utumno was destroyed and Melkor brought in chains to Valinor. The Valar also summoned the Elves to dwell in their land, and many answered this summons.
A period of three ages (about 2,900 years) followed. Melkor was imprisoned in the halls of Mandos, and the Valar and Eldar dwelt together in the light of the Trees. In the darkness of Middle-earth, the Dark Elves who had not journeyed to Valinor still dwelt, and the Fathers of the Dwarves stirred. Men would not appear until some time after the end of the Years of the Trees.
These Years came to an end when ManwÃ« released Melkor from his imprisonment. For a time, the Dark Lord pretended friendship with the Eldar, but he turned back to the darkness. With Ungoliant, he destroyed the Trees, stole the Silmarils and fled back to the north of Middle-earth. Seeking revenge, FÃ«anor led a great part of the Noldor out of Valinor and back to Beleriand.
So the Years of the Trees came to an end. At this time, the Valar made the Sun and Moon to give light to the World, and the Years of the Sun began, and with them the First Age.