Book excerpt: The day of the Lord is not just a future event. Many people regard the day of the Lord as a future reality with little relevance for the earthly life of believers. But the apostle Paul understood the theological concept differently. For him the day of the Lord was a matter of present experience that influenced every aspect of his theology. In The Righteous and Merciful Judge, authors Matthew Aernie and Donald Hartley issue a corrective to scholarship that misconstrues the day of the Lord as only a distant event. Through engagement with scholarship and careful exegesis of relevant texts, they argue that the concept of the day of the Lord was so significant for Paul that every aspect of his theology was in some way affected by it. Aernie and Hartley show us that Paul's understanding of the day of the Lord relates to all of Paul's theology precisely because it was shaped by his encounter with Jesus, the Lord himself. The day of the Lord is coming, but it already shapes our lives and theology. The Righteous and Merciful Judge demonstrates that the day of the Lord is transformative and influential for believers today, just as it was for Paul.