Interesting poem. I can't decide if Byron is referring to the apocalypse or the end of his marriage. At first glance, I would say the former. The biblical language used reinforces this. However, after finding that his wife divorced him shortly before he wrote this, I'm leaning toward the latter. Line 2 says "the bright sun was extinguished, and the stars did wander darklilng in the eternal space". On the surface, this could refer to the clouds covering the sun or the end of the world as the critics suggest. But, by looking a little deeper, this could be a reference to his ex-wife, the end of his love. Maybe, the poem could even be a combination of the two.
The form of the poem is interesting as well. It is written in unrhymed iambic pentameter, but it isn't seperated into stanzas, and it comes out as one big run-on thought. This could be a way to reflect the panic that would most likely come with the end of everything.