Symbolism of Sunset in Literature

In the excerpt below, the author describes a sunset:

As the sun descended, it dipped beneath a horizon smeared with hues of orange and purple, casting a radiant glow that seemed to blanket the world in the promise of dreams. Birds scattered like shadows in the fading light, while the trees, silhouetted against the vibrant sky, stood as timeless sentinels guarding the last whispers of day.

Considering the passage and the use of symbolism, what does the 'sunset' primarily represent in this context?