Therefore at such a time the prudent person keeps silent, for it is an evil time. Alas, you who are longing for the day of the Lord, For what purpose will the day of the Lord be to you? It will be darkness and not light;
Amos 5:13,18 NASB
Anyone who is longing for the day of the Lord must know for what purpose this day will be to you. One must understand that it is coming in darkness and is accompanied by destruction. Joel says that multitudes will be in the valley of decision as that day approaches. Will it be your decision to trust completely in Christ?
22 Many will say to Me on that day, ‘Lord, Lord, did we not prophesy in Your name, and in Your name cast out demons, and in Your name perform many miracles?’ 23 And then I will declare to them, ‘I never knew you; depart from Me, you who practice lawlessness.’
Matthew 7:22-23 NASB
Jesus had said that men’s hearts would fail them for what is coming upon the earth. And though He does not say it, it would appear that He is speaking of the time of Tribulation, which He says will be followed by the days of darkness caused by the Sun Moon and stars ceasing to shine. This condition will come before the day of the Lord as seen in both chapters 2&3 of Joel, and in Isaiah 13, And Jesus repeats that scenario to us announcing His coming.
So Amos says that Men are not to long for the Day of the Lord without considering its meaning for them, because it will follow a falling away for many and devastation for Israel as 2/3rds of her people die according to Zechariah leading into this day, which we see begins in darkness. The day of the lord is that long 1000 year day when every man will be judged.
For believers who are in Christ, our reward is to rule with Him during this 1000 years, and then to enter into the New Jerusalem.
For evil men and worshipers of the Beast and his system of government and religion there will be a judgment to the lake of fire.
For the dead who were not raised in the first resurrection because they are not a part of the body and bride of Messiah (Christ), there will be judgment before the Great White Throne of God. These will be judged from the books, including the book of life. The persons who’s names are not found in the book of life will be cast into the lake of fire.
Why is the book of life brought out at this judgment following the millennium? The nations who enter the millennium will be judged at its beginning as to their worthiness to remain, and those who helped Messiah’s brethren will be granted entrance as nations to be ruled by Messiah and His bride. These are unsaved Nations who may repent and not have their names blotted from the Lamb’s book of life. The book must be present for this judgment.
The day of the Lord is 1000 years of Christ’s rule with His rod of iron, and includes his judgment. It is not a day to be longed for if one is not abiding in Him. Ones trust cannot be in oneself it must be in Him alone.
But as many as received Him, to them He gave the right to become children of God, even to those who believe in His name, who were born, not of blood nor of the will of the flesh nor of the will of man, but of God.
John 1:12-13 NASB