The Bible promises a seven-year period of Tribulation on Earth, but the final judgment moment for unbelievers waits for another 1,000 years. So why does God bother with bringing Tribulation on earth? What does it accomplish?
The seven year Tribulation is an important period in God's plan for the earth. We learn of the seven year period of Tribulation and God's purposes in bringing it primarily from the Old Testament prophets, particularly Daniel:
In Daniel 9, we learn three important details regarding the coming time of Tribulation. First, we learn that this period of time last one "week" (or literally "seven" in Hebrew). By the context of the historical events described in Daniel 9, it becomes clear that Daniel means a seven-year period of time.
Daniel says a total of seventy "sevens" (i.e., 490 years) have been decreed by God. Based on the timing of events Daniel provides in vs.25-26, we can see that 69 of of the 70 sevens have already transpired, leaving just one seven year period remaining. That remaining seven year period is the period of Tribulation, which has yet to happen.
Secondly, Daniel tells us God designated this period of 490 years for Daniel's "people." In other words, this is a period for Israel. Israel refers to the nation descended from Abraham and bound to the Old Covenant. By these terms, the Church is not "Daniel's people," so the Church is specifically excluded from the events of this 490 year period. This period began in 605 BC before the church was formed, and it was suspended when the Messiah was "cut off." Therefore, the church has never experienced any part of the 490-year period designated for Israel...nor will it ever!
Thirdly, we learn the purposes God has for Israel during this period. In v.24 Daniel says the 490 years were decreed for six reasons:
1. To finish the transgression - to bring Israel's disobedience to the Old Covenant to an end
2. To make an end of sin - to put an end to all sin in the people of Israel (i.e., to glorify Israel)
3. To make atonement for iniquity - to exact a price for Israel's sins under the terms of the Old Covenant
4. To bring in everlasting righteousness - to usher in the Milennial Kingdom on earth
5. To seal up vision and prophecy - to bring to an end all revelation by granting a full knowledge of God
6. To anoint the most holy place - to set up the Milennial Kingdom temple where Christ will reside
Notice that all these purposes and outcomes are focused exclusively on preparing Israel to enter the Kingdom following Tribulation at Christ's Second Coming. This is further confirmation that this period of great distress on the Earth is focused entirely on Israel and not on the church. The extreme nature of the events during Tribulation impact the whole earth, but the intended target is Israel.
We find even more confirmation of this conclusion in Jeremiah's description of the Tribulation, when he labels it a "time of Jacob's (i.e., Israel's) distress:"
Tribulation is called a time of Israel's distress, and yet Jacob (i.e., the nation of Israel) will be saved from it. Therefore, the chief purpose of Tribulation is to bring Israel back to the Lord, as Ezekiel teaches:
The Lord promises to bring Israel through a time of judgment and inspection (i.e., passing under the rod) so that He may purge Israel's sin and rebellion thereby bringing them back into the bond of the covenant. The covenant mentioned in this verse is the Old Covenant delivered through Moses.
By the terms of that covenant, Israel must experience 490 years of God's judgment for failing to keep the covenent terms. Tribulation is the final act of that judgment, and it will result in bringing Israel back to the Lord. (You can learn much more about how God accomplishes this miraculous work by taking our Revelation course.)
Having learned the true purpose of Tribulation, we can see why the Church does not experience this period of history when it arrives. Since this period is appointed for Israel, the Church will be removed prior to the beginning of the final seven years of God's judgment. This is why Paul says the Lord will return to remove the church prior to the beginning of the Tribulation:
You can read more about the nature and timing of the rapture of the Church in our Revelation study and by reading Explaining the Rapture.