Edit: Or am I just blind and that quote has always been there?

I have never personally heard of this poem/quote before, but it sounds very interesting. I'd like to say that I have quite a bit of knowledge on christianity, but I have lost some over the past few years. Would you suggest to read The Second Coming or learn more about W.B Yeats? I'd love to hear more about him! As for the speculation on why Chisnell were to post the quote, although I haven't read the quote I wonder if the theme would have anything to do with Flatland or Invisible Man. 

This poem is definitely referring to Revelation. Aside from the name that is clearly about the second coming of Christ, there are several examples of things right out of the book of Revelation: anarchy, a "blood-dimmed tide", loss of conviction and innocence, beasts with the body of a lion and head of man (a combination of two creatures in front of God's throne in Heaven in Revelation (also I feel like I remember a description of a creature similar to this that comes to Earth at the end of the Tribulation, but I can't find where the Bible says that, so either I'm falsely remembering something, or I'm just bad at finding things)), and many more examples. But I think the point you made that this was written right after WWI is really important. The WWI era was a crazy time and probably felt pretty chaotic. It's kind of like how people are feeling about 2020- I'm sure we've all heard plenty of people say that we've had a whole decade of events happening in one year. I'm sure people felt a similar way back then, too! They had WWI, which left a lot of the world in a not very good place, their own pandemic to deal with, which killed 50 million people of the roughly 2 billion person population. Yeats was probably observing the world around him which seemed to be falling apart and speculating about the second coming and Tribulation happening soon after. This is something that I have heard people say even this year with all that has gone on in 2020, so I find it very plausible that this is what Yeats was getting at.

I haven't ever heard of this poem until now, but I thought it was an interesting one to read. Although my knowledge of Christianity is very limited (which led me to have to read it 4 times over just to make sure I actually understood) I thought it was interesting. I do know that 'The Second Coming' is a reference/prophecy in multiple religions of Jesus' return. This poem also speaks of a revelation, so perhaps W.B. Yeats is saying during the second coming of Jesus there will be a revelation along with it?

@klynnph The revelation in the poem refers to the book of Revelation in the Bible. Revelation is the last book of the Bible where the second coming of Christ is laid out. While the Rapture (when Jesus will take all His people to Heaven) and Tribulation (seven years following the Rapture (actually people disagree on whether the Rapture is before, in the middle of, or after the Tribulation, but that's irrelevant in this discussion) where many supernatural and devastating events will occur before God establishes His kingdom on Earth) are talked about and prophesied throughout the Bible, Revelation contains the most and most detailed information about these times. Revelation received its name because it is referring to God revealing Himself and His purposes for Earth and the life on it when Jesus returns and God establishes His kingdom on Earth. So when Yeats said that a revelation and "the Second Coming [are] at hand", he was alluding to the book of Revelation and his observations of the world suggesting that he believes these events are soon to happen.