What does Revelation 9:15 mean?
Prior verses indicated these beings were "bound," meaning they are fallen angels, or demons. This verse reports that the four angels had been prepared precisely for the time of their release. The words, "the hour, the day, the month, and the year" are not intended to be added together into some exact amount of time. Rather, this expression means God had prepared them for this precise instant of their release—for this exact moment in history.The purpose of these demons' release was to kill one third of mankind. Daniel 12:1 predicts this terrible time. It states: "And there shall be a time of trouble, such as never has been since there was a nation till that time." Also, this level of catastrophe was part of what Jesus predicted, calling it a great tribulation. Matthew 24:21–22 records His words: "For then there will be great tribulation, such as has not been from the beginning of the world until now, no, and never will be. And if those days had not been cut short, no human being would be saved. But for the sake of the elect those days will be cut short."
Jesus' words are not entirely symbolic. The fourth seal judgment (Revelation 6:7–8) released the "pale" horseman who caused the death of one fourth of earth's people. This sixth trumpet judgment slays one third of those who survive, meaning the apocalypse has already killed half of the pre-tribulation population. Death on that scale, in only a few years, would eventually lead to human extinction, if not held in check by God.