There are three groups of people on the earth, three thrones of judgment and three great tribulations mentioned in the Bible.
Many Christians seem to be familiar with only one great tribulation. This would appear to be the root cause of the division in opinion regarding the timing of the rapture of the church.
Each of the three groups has a great tribulation period peculiar to it. Although each great tribulation will affect the whole world at varying degrees, it will be particularly devastating for each targeted group.