"Then they will deliver you to tribulation, and will kill you,
and you will be hated by all nations because of My name.
At that time many will fall away and will betray one another
and hate one another. Many false prophets will arise and will
mislead many. Because lawlessness is increased, most
people's love will grow cold. But the one who endures
to the end, he will be saved." (Matt 24:9-13 NASB)
When the Lamb broke the fourth seal, I heard the voice
of the fourth living creature saying, "Come."
I looked, and behold, an ashen horse; and he who sat on it
had the name Death; and Hades was following with him.
Authority was given to them over a fourth of the earth,
to kill with sword and with famine and with pestilence
and by the wild beasts of the earth.
When the Lamb broke the fifth seal, I saw underneath
the altar the souls of those who had been slain because of
the word of God, and because of the testimony which they
had maintained. (Rev 6:7-9 NASB)
This is most likely at the mid point of the "70th week of Daniel" (Dan 9:25-27), where the Antichrist breaks a covenant he makes with Israel, and unleashes his fury against them. Other passages that correspond to this point in time are found in Daniel 7:7-8, 20-21, 24-25, which speak of the rise of the "little horn" who persecutes the saints of the Highest One for "a time, times, and half a time" (31/2 years). This is also mentioned in Daniel 8:23-26, and Daniel 11:31-36, where we see the abomination of desolation is set up, something Jesus warns us about as well in Matthew 24:15-22, as the point when the great tribulation begins. According to Jesus, this period of time will be a horrific time unlike any other that has been, or will be (Matt 24:21-22), and for the sake of the elect, it will be shortened.
We read in Revelation 12:7-17 of a war in heaven, where the serpent, also called Satan, is cast down to the earth. This results in a time of terrible persecution against Israel, and upon Christians as well (see Rev 12:17). Again, in verse 14, we read that this time of tribulation lasts for a time, times, and half a time. Just like we read in Daniel 7, it is for a time frame of 3 1/2 years.
Revelation 13 speaks of the rise of the "beast", which is not only the Antichrist, but also his kingdom, made up of ten nations. It is my belief that at the point Satan is cast down to the earth, he enters this Antichrist and uses the "beast" as an agent of his wrath.
Here we read of the beast given a mouth speaking blasphemy (see also 2 Thess 2:3-6), and authority for 42 months, or 3 1/2 years (Rev 13:4-7). Just as we saw in Daniel's prophecy, this beast will make war with the saints and overcome them, and just as Jesus stated, It will be the one who endures to the end who will be saved (Matt 24:13).
Then I heard a loud voice in heaven saying,
"Now the salvation, power, and the kingdom
of our God and the authority of His Christ
have come, for the accuser of our brethren
has been thrown down, he who accuses them
before our God day and night.
And they overcame him because of the
blood of the Lamb and because of the word
of their testimony, and they did not love
their life even when faced with death."
Revelation 12:10-11 NASB.