To warn of judgment day on May 21 2011.

When we look at the sending forth of the Gospel during the church age, we must take note of the two witnesses of Revelation 11. These two witnesses represent the true believers. Initially, they identify with the true believers in the churches during the church age. The command to go into all the world with the Gospel had been given at the beginning of the church age. The carrying out of this command was typified by the two witnesses of which the Bible speaks in Revelation 11. Revelation 11:3,4 declares:

And I will give power unto my two witnesses, and they shall prophesy a thousand two hundred and threescore days, clothed in sackcloth. These are the two olive trees, and the two candlesticks standing before the God of the earth.

The two witnesses are identified in Revelation 11:4 as two olive trees and two candlesticks. The two olive trees identify with the olive tree of Romans 11:16-24. This underscores that these two witnesses represent true believers.
The two witnesses identify with the two candlesticks. This immediately identifies with the church age. Revelation 1:20 and Revelation 2:1 teaches us that symbolically, each church is represented by a candlestick amongst which Christ walks. The candlestick represents the light of the Gospel as it is sent out into the world during the church age by the churches and during the latter rain by the true believers who are altogether outside of the churches.
The number two (two witnesses, two olive tree, two candlesticks), identifies with true believers who faithfully bring the Gospel. Remember Jesus sent the twelve disciples out two and two (Mark 6:7) and the seventy two and two (Luke 10:1).
We see the end of the church age in the death of these two witnesses, as we read Revelation 11:7, which declares:

And when they shall have finished their testimony, the beast that ascendeth out of the bottomless pit shall make war against them, and shall overcome them, and kill them.

The death of the two witnesses identifies with the destruction of the church. Satan is loosed at the beginning of the Great Tribulation and is allowed by God to destroy the churches.

There are 93 days left,it is still the day of salvation!