The church age and the Olivet Discourse

 During the Lord's first earthly ministry, He told His disciples many things regarding the coming destruction of Jerusalem, of the tribulation that is yet to occur, and of His coming kingdom.  Most of His discussion on this occurred while he taught on the Mount of Olives, which is why it these teachings are called the Olivet Discourse, Matthew 24, Matthew 25, Mark 13, and Luke 21.  However, some teaching on these subjects occurred at other times as explained in this site in the examination of Luke 17.  The Lord warned His disciples, and to the church through them, to expect an increase in natural and manmade troubles that the world would experience as time marched toward the beginning of the tribulation.  As shown in the next graphic, there is a building up of the number of occurrences, duration, and intensities in the natural violence and wars that men would suffer with the approach of the seven years of tribulation.  

Source: http://www.thesecondcomingofchrist.org/survey_of_timelines-for-interp.htm#7