@Rockerduck yes I was asking about the first 3.5 years, I do not believe the great tribulations start until the antichrist is actually revealed and I think the two witnesses come in the first half, not sure.
Regarding your post #138 - the Antichrist presents himself after the first 3 1/2 yrs. He ushers I the Great Tribulation...the next 3.5 yrs.
Chapter 10 -- the little book and then chapter 11 -- first three verses. The two witnesses and how they will be dressed and what they will be doing. Vs 4 talks about the two olive trees and the two lampstands standing before the God of the earth. Then look at Zechariah 4: 1-3 and then vs 11-14.
As for the When -- can't really tell.