The Ministry Of The Two Witnesses

Q. I am interested in the chronology of the events in Revelation. We know the abomination of desolation occurs at the mid point of the tribulation. When do the two prophets start their ministry?

A. The two witnesses are first introduced in Rev. 11, two chapters before the beginning of the Great Tribulation on Earth.  This tells us that their ministry begins in the lull between the 6th and 7th trumpets and ends just prior to the 2nd Coming.