Evening, a time when the light and heat are fading away, represents a state in which a person -- or a community of people -- is turning away from the Lord, with little desire left to be good and little knowledge left regarding what good is. Evening is often a time of judgment.

In Genesis 19:1, the evening signifies the visitation that comes before judgment. (Arcana Coelestia 2318)

In Genesis 30:16, this signifies the good or truth in a state of good, but in the obscurity that is characteristic of the natural. (Arcana Coelestia 3949)

'To open,' as in Revelation 9, signifies communication and conjunction.

(References: Apocalypse Explained 537)