Every time the phrase the four corners of the earth occurs in the Bible it's in the context of the Millennial Kingdom, which is after the plagues of the tribulation.
Four Corners of the Earth in Context
November 4th
The First plague of the tribulation is a curse upon the land. The stars begin to fall as burning hail causing a caustic smog which affects people and animals as a noisome and grievous sore. The land burns.