Study
18 And to rule over the day and over the night, and to divide the light from the darkness: and God saw that it was good.
'To open,' as in Revelation 9, signifies communication and conjunction.
(References: Apocalypse Explained 537)
2 A day of darkness and gloominess, a day of clouds and thick darkness. As the dawn spreading on the mountains, a great and strong people; there has never been the like, neither will there be any more after them, even to the years of many generations.