Will the Rapture happen before the 7-year Tribulation Period, where God pours out His judgments on the earth (Rev. 6-19)? I believe so. In Rev. 4, the apostle John is caught up into heaven and what he sees is interesting. Here are some clues that rapture takes place at this time.
1.He is seeing something happening in the future. Jesus tells him "I will show you what must take place after these things" (Rev. 4:1). What he is about to see is something that will take place in the future.
2.A door is open in heaven (Rev. 4:1). John has already seen Jesus in all His glory in heaven in Rev. 1:12-16, so why is it necessary for a door to be open in heaven? Many Bible scholars believe the door opens to let the Church in at the rapture. The next time heaven is opened is Rev. 19:11-14 and His Church is following Him out. Presumably the Church goes in at Rev. 4:1 and comes out in Rev. 19.
3."Come up here" (Rev. 4:1) This phrase is also used in Rev. 11:12 when the two prophets are killed, then resurrected, and ascend into heaven. "Come up here" could mean the Church is being called into heaven in Rev. 4:1.
4.The 24 elders are wearing crowns (Rev. 4:4). After John gets caught up into heaven, he sees 24 elders around the thrones wearing crowns on their heads. Why is this significant? Because Christians will be rewarded at the rapture. The rapture is a resurrection of those who have died in Christ (1 Thess. 4:16-17). Jesus said, "You will be repaid at the resurrection of the righteous" (Luke 14:14). Peter said the crowns would be given out at the rapture (1 Pet. 5:4). Paul also said he would receive a crown at the rapture (2 Tim. 4:8). No one in heaven has been rewarded at this time. So if John is looking into the future and sees 24 elders wearing crowns, it must mean the rapture has taken place.
5.The Tribulation doesn't begin until Revelation 6. John sees that the elders have been rewarded in Rev. 4, and then Jesus takes the scroll in Rev. 5, and He breaks the seals on the scroll in Rev. 6, which starts the Tribulation Period. This shows the rapture happens before the tribulation, which means a "Pre-Tribulation" rapture.
To hear the entire message on this subject, go to http://www.churchoflivingwater.net/node/23 and click on "The Pre-Tribulation Rapture."