The 'sun' in the Word, when referring to the Lord, signifies His divine love and wisdom. Because the sun represents the Lord, with respect to His divine love wisdom, since ancient times even to the present day, worship is done and temples are built facing the rising sun. The sun signifies celestial and spiritual love and also the Lord regarding His divine love, and so the good of love from Him. In the opposite sense, it signifies a denial of the Lord's divinity, and so adulteration of the good of love.

In Genesis 15:12, 19:23, this signifies the time and state before consummation; for the sun signifies the Lord, and the celestial things of love and charity; so its setting represents the last time of the church. Its rising signifies a coming of the Lord, and the first period of a new church. (Arcana Coelestia 1837, 1859)

In Jeremiah 8:1, this signifies self-love and its lusts. (Arcana Coelestia 2441)

In Revelation 12:1, this signifies love. (Arcana Coelestia 253, Arcana Coelestia 3272[2])

Sun signifies the good of love. (Arcana Coelestia 4918[3]）

(Referencat: Apocalypse Explained 709)

1859. That 'the sun went down' means the final period when the close came is clear from what has been stated above at verse 12 about the sun going down and about what that means, namely the final period of the Church.