Q. When do the two witnesses do their 1260 day prophesying during the 7 year tribulation period? The 1st half, the second half or some part of both?
A. According to my understanding, the two witnesses of Rev. 11:3 will appear shortly before the beginning of the Great Tribulation, which will begin on Earth in Rev. 13 following the expulsion of the dragon (Satan) from Heaven. We can tell they arrive prior to the Great Tribulation because John was told to count the worshipers in the Temple (Rev. 11:1), and when the Abomination of Desolation which kicks off the Great Tribulation occurs, the Temple will be rendered unfit for worship. Since their time of ministry is the same length as the Great Tribulation that would mean they will be put to death shortly before its end.