Formal or literary term for the sun as it sets in the evening. The more common word is 夕日 (ゆうひ).
See also: 夕日 (ゆうひ)
The setting sun dyed the western sky red.
Formal or literary term for the time of day when the sun is setting. In modern Japanese, 夕方 or 夕暮れ are more common.
At dusk, the town grows quiet.
The reading せきよう is the on'yomi of the kanji 夕 (せき) and 陽 (よう), used in formal or literary contexts. The same kanji are more commonly read ゆうひ (kun'yomi) with the same meaning.