The The Day of the Lord, in prophetic writing, is the day of judgment when God will intervene directly in world affairs. As described in Zephaniah, for instance, God will sweep everything away. In Matthew's gospel God is described as gathering the elect on the day... will be a time for God’s final judgment on both the innocent and the guilty.
What will the Day of the Lord be like? The world is a mess in many ways. There is too much hurt, violence, wars, sickness, and, of course, there is death. Justice is certainly lacking when innocent people suffer at the hands of wicked people who prosper. Someday, somehow, God will need to act to fix this if God is going to remain faithful to God’s promises. The time when God finally acts to vindicate the innocent and punish the wicked is called the Day of the Lord.
Pious folks often look forward to this day, assuming that they will be rewarded and their tormentors will get what is coming to them. The prophets, like Prophet to the northern kingdom who condemned Israel's oppression of the poor, calling for justice to "roll down like waters." and Joel, warn God’s people to be cautious, not to hope for something that could turn out to be a judgment on them as well as their enemies. The Day of the Lord can be a good thing or a bad thing, depending on whether one receives a positive or a negative judgment. Some people long for it when they should dread it, and vice versa. Joel sees the locust plague as a negative example of the Day of the Lord. Later in the book, when Joel is talking about the end-time, he sees this dreaded day as a good time for Israel and a bad time for all the nations who have sinned against God and God’s people.
An important statement about God appears in 2:13. In the midst of discussions about a God who punishes, it is important to note the bottom line about God. God is gracious and merciful, slow to anger, and abounding in The steadfast love (hesed) of God is the assurance of God's loving kindness, faithfulness, and mercy. This assurance rings throughout the Old Testament, and is affirmed more than 120 times in the Psalms. In some hymns of praise the response of the people was likely.... This is a common description of God that is found elsewhere in the Bible. Further, God relents from punishing. The word “relent” can be translated in a number of ways. The basic meaning is something like this: out of compassion, God changes God’s mind. God never wants to punish and will, in fact, cancel the punishment if people provide some good reason to do so, such as true repentance or a change of behavior.