Behold, I will send you Elijah the prophet before the great and awesome day of the LORD comes. --Malachi 4:5
The Day of the Lord refers to God’s special interventions into the course of world events to judge His enemies, accomplish His purpose for history, and thereby demonstrate who He is — the sovereign God of the universe (Isa. 2:1–2; Ezek. 13:5, 9, 14, 22–23; 30:3, 8, 19, 25–26).
Evidence for this significance of the Day of the Lord is found in references in the Scriptures to past Days of the Lord. The Bible indicates that there have been several past Days of the Lord in which God exercised and demonstrated His sovereign judgment on other nations. He raised up Assyria to judge the northern kingdom of Israel during the 700s B.C. (Amos 5:18, 20), Babylon to judge the southern kingdom of Judah during the 600s and 500s B.C. (Lam. 1:12; 2:1, 21–22; Ezek. 7:19; 13:5; Zeph. 1:7–13; 2:2–3), Babylon to judge Egypt and its allies during the 500s B.C. (Jer. 46:10; Ezek. 30:3), and Medo-Persia to judge Babylon during the 500s B.C. (Isa. 13:6, 9). (links and notes in AV article -- mushroom)Notice the word that keeps popping up in there -- sovereign.
There are times in history as there will be times in the future when God intervenes more directly than He does on a day to day basis, not just in the miraculous change of an individual life, but in the very course of world events. It could be, for example, that September 11, 2001 was the beginning of a day of judgment for America, and, perhaps, the West in general. God does not necessarily endorse the belief systems or worldviews of those He allows to chasten His people. Babylon, Assyria, and Rome were all secular powers antagonistic toward the God of Abraham, Isaac, and Jacob. Islam is primarily a tyrannical political system that empowers religiously-garbed despots. As such, it is in conflict with the concepts of personal liberty, individualism, and innovation. It is generally not compatible with Christianity, Judaism, or other major religions – including its own branch of personal, mystical practice, Sufism.
As the above quote from Showers indicates, those raised up by God to render judgment will themselves be judged, perhaps more harshly and destructively for their lack of mercy as instruments of divine wrath.
These days they call these interventions “black swans”, and it is correctly stated that one never sees a black swan until one does. When the Day comes, whenever it comes, whatever form it takes, however catastrophic it may be, the one thing to remember is that your Father is in control.
See that you do not refuse him who is speaking. For if they did not escape when they refused him who warned them on earth, much less will we escape if we reject him who warns from heaven. At that time his voice shook the earth, but now he has promised, “Yet once more I will shake not only the earth but also the heavens.” This phrase, “Yet once more,” indicates the removal of things that are shaken—that is, things that have been made—in order that the things that cannot be shaken may remain. Therefore let us be grateful for receiving a kingdom that cannot be shaken, and thus let us offer to God acceptable worship, with reverence and awe, for our God is a consuming fire. (Hebrews 12:25-29)