"What is the Tribulation? How do we know the Tribulation will last seven years?"

The Tribulation is a future 7-year period of time when God will finish His discipline of Israel and finalize His judgment of the unbelieving world. The Church, made up of all who have trusted in the person and work of the Lord Jesus to save them from being punished for sin, will not be present during the Tribulation. The Church will be removed from the earth in an event known as the Rapture (1 Thessalonians 4:13-18; 1 Corinthians 15:51-53). The Church is saved from the wrath to come (1 Thessalonians 5:9). Throughout Scripture, the Tribulation is referred to by other names such as these:

1) The Day of the Lord (Isaiah 2:12; 13:6, 9; Joel 1:15, 2:1, 11, 31, 3:14; 1 Thessalonians 5:2)
2) trouble or tribulation (Deuteronomy 4:30; Zephaniah 1:15)
3) Great Tribulation, which refers to the more intense second half of the 7-year period (Matthew 24:21)
4) time or day of trouble (Daniel 12:1; Zephaniah 1:15)
5) time of Jacob's trouble (Jeremiah 30:7)

An understanding of Daniel 9:24-27 is necessary in order to understand the purpose and time of the Tribulation. This passage speaks of 70 weeks that have been declared against "your people." Daniel's "people" are the Jews, the nation of Israel, and what Daniel 9:24 speaks of is a period of time that God has given "to finish the transgression, to make an end of sin, to make atonement for iniquity, to bring in everlasting righteousness, to seal up vision and prophecy, and to anoint the most holy place." God declares that "70 weeks" will fulfill all these things. It is important to understand that when "70 weeks" is mentioned, it is not speaking of a week as we know it (7 days). The Hebrew word (heptad) translated as “week” in Daniel 9:24-27 literally means "7" and 70 weeks literally means “70 sevens” (70 times 7). This time period of which God speaks is actually 70 sevens of years, or 490 years. This is confirmed by another part of this passage in Daniel. In verses 25 and 26, Daniel is told that the Messiah will be cut off "7 weeks and 62 weeks" (69 weeks total) after the decree to rebuild Jerusalem. In other words, 69 sevens of years (483 years) after the decree to rebuild Jerusalem, the Messiah will be cut off. Biblical historians confirm that 483 years passed from the time of the decree to rebuild Jerusalem to the time when Jesus was crucified. Most Christian scholars, regardless of their view of eschatology (future things/events), have the above understanding of Daniel's 70 weeks.

With 483 years having passed from the decree to rebuild Jerusalem to the cutting off of the Messiah, this leaves 1 seven (7 years) to fulfill the terms of Daniel 9:24. This final 7-year period is known as the Tribulation period--it is a time when God finishes judging Israel for their sin.

Daniel 9:27 gives a few highlights of the 7-year Tribulation period. This verse says, "And he will make a firm covenant with the many for one week, but in the middle of the week he will put a stop to sacrifice and grain offering; and on the wing of abominations will come one who makes desolate, even until a complete destruction, one that is decreed, is poured out on the one who makes desolate." The person of whom this verse speaks is the person Jesus calls the "abomination that makes desolate" (Matthew 24:15) and is called “the beast” in Revelation 13. Daniel 9:27 says that the beast will make a covenant for 1 week (7 years), but in the middle of this week (3 1/2 years into the Tribulation), he will break the covenant, putting a stop to sacrifice and grain offering. Revelation 13 explains that the beast will place an image of himself in the temple and require the world to worship him. Revelation 13:5 says that this will go on for 42 months, which is 3 1/2 years. Since Daniel 9:27 says that this will happen in the middle of the week, and Revelation 13:5 says that the beast will do this for a period of 42 months, it is easy to see that the total length of time is 84 months or 7 years. Also see Daniel 7:25 where the "time, times, and half a time" (time=1 year; times=2 years; half a time=1/2 year; total of 3 1/2 years) also refers to the Great Tribulation, the last half of the 7-year Tribulation period when the "abomination that causes desolation" (the beast) will be in power.

For further references about the Tribulation, see Revelation 11:2-3 which speaks of 1,260 days and 42 months, and Daniel 12:11-12 which speaks of 1,290 days and 1,335 days, all of which have a reference to the midpoint of the Tribulation. The additional days in Daniel 12 may include time at the end for the judgment of the nations (Matthew 25:31-46) and time for the setting up of Christ's millennial kingdom (Revelation 20:4-6).