What is the effect of the gospel in the world?

Thanksgiving for the Chosen
Thanksgiving for the Love of God
Thanksgiving for the Gospel

The LORD announced a period for the repentance of Israel that would come in the "last/latter days" (Deuteronomy 4; 30), the prophet Obadiah announced the coming judgment on all nations at the Day of the LORD (Obadiah 15), Joel prophesied that Israel would also be judged on the Day of the LORD but whoever called on the name of the LORD would be saved (Joel 2:28-32), then Jesus told the apostles that they and the coming Church would be His witnesses (Acts 1:8) and, with the coming of the Holy Spirit, Peter announced the inauguration of the last days and the need to repent for the coming Day of the LORD, with Jesus Christ the Lord on whom Israel must call (Acts 2).

What is the proof or witness that the Day of the LORD is coming?

The Church.

The success of the gospel in the world, the existence of the Church, and the example and sanctification of the Church usher in the Day of the LORD (1 Thessalonians)

https://youtu.be/Taijqzdo8_c