We can assume Jesus spoke of these things chronologically in Matthew 24. If that is the case, it appears Satan's personation will happen after probation closes. What say you?
Mat 24:7 For nation shall rise against nation, and kingdom against kingdom: and there shall be famines, and pestilences, and earthquakes, in divers places.
Mat 24:8 All these are the beginning of sorrows.
Mat 24:9 Then shall they deliver you up to be afflicted, and shall kill you: and ye shall be hated of all nations for my name's sake.
Mat 24:10 And then shall many be offended, and shall betray one another, and shall hate one another.
Mat 24:11 And many false prophets shall rise, and shall deceive many.
Mat 24:12 And because iniquity shall abound, the love of many shall wax cold.
Mat 24:13 But he that shall endure unto the end, the same shall be saved.
Mat 24:14 And this gospel of the kingdom shall be preached in all the world for a witness unto all nations; and then shall the end come.
Mat 24:15 When ye therefore shall see the abomination of desolation, spoken of by Daniel the prophet, stand in the holy place, (whoso readeth, let him understand:)
Mat 24:16 Then let them which be in Judaea flee into the mountains:
Mat 24:17 Let him which is on the housetop not come down to take any thing out of his house:
Mat 24:18 Neither let him which is in the field return back to take his clothes.
Mat 24:19 And woe unto them that are with child, and to them that give suck in those days!
Mat 24:20 But pray ye that your flight be not in the winter, neither on the sabbath day:
Mat 24:21 For then shall be great tribulation, such as was not since the beginning of the world to this time, no, nor ever shall be.
Mat 24:22 And except those days should be shortened, there should no flesh be saved: but for the elect's sake those days shall be shortened.
Great time of trouble such as never was.
Mat 24:23 Then if any man shall say unto you, Lo, here is Christ, or there; believe it not.
Mat 24:24 For there shall arise false Christs, and false prophets, and shall shew great signs and wonders; insomuch that, if it were possible, they shall deceive the very elect.
Mat 24:25 Behold, I have told you before.
Mat 24:26 Wherefore if they shall say unto you, Behold, he is in the desert; go not forth: behold, he is in the secret chambers; believe it not.
Mat 24:27 For as the lightning cometh out of the east, and shineth even unto the west; so shall also the coming of the Son of man be.
I do not think that you can take these verses chronologically. For one thing, Jesus is talking about two different events. And some of the things apply to both events.
The tribulation spoken of in verse 22, that is shortened for the elect's sake, is the persecution that took place during the dark ages. After that tribulation, it says in verse 29, the sun was darkened, and the moon did not give her light, and the stars fell.
From the destruction of Jerusalem, Christ passed on rapidly to the greater event, the last link in the chain of this earth's history,--the coming of the Son of God in majesty and glory. Between these two events, there lay open to Christ's view long centuries of darkness, centuries for His church marked with blood and tears and agony. Upon these scenes His disciples could not then endure to look, and Jesus passed them by with a brief mention. "Then shall be great tribulation," He said, "such as was not since the beginning of the world to this time, no, nor ever shall be. And except those days should be shortened, there should no flesh be saved: but for the elect's sake those days shall be shortened." For more than a thousand years such persecution as the world had never before known was to come upon Christ's followers. Millions upon millions of His faithful witnesses were to be slain. Had not God's hand been stretched out to preserve His people, all would have perished. "But for the elect's sake," He said, "those days shall be shortened." {DA 630.5}
Now, in unmistakable language, our Lord speaks of His second coming, and He gives warning of dangers to precede His advent to the world. "If any man shall say unto you, Lo, here is Christ, or there; believe it not. For there shall arise false christs, and false prophets, and shall show great signs and wonders; insomuch that, if it were possible, they shall deceive the very elect. Behold, I have told you before. Wherefore if they shall say unto you, Behold, He is in the desert; go not forth: behold, He is in the secret chambers; believe it not. For as the lightning cometh out of the east, and shineth even unto the west; so shall also the coming of the Son of man be." As one of the signs of Jerusalem's destruction, Christ had said, "Many false prophets shall rise, and shall deceive many." False prophets did rise, deceiving the people, and leading great numbers into the desert. Magicians and sorcerers, claiming miraculous power, drew the people after them into the mountain solitudes. But this prophecy was spoken also for the last days. This sign is given as a sign of the second advent. Even now false christs and false prophets are showing signs and wonders to seduce His disciples. Do we not hear the cry, "Behold, He is in the desert"? Have not thousands gone forth into the desert, hoping to find Christ? And from thousands of gatherings where men profess to hold communion with departed spirits is not the call now heard, "Behold, He is in the secret chambers"? This is the very claim that spiritism puts forth. But what says Christ? "Believe it not. For as the lightning cometh out of the east, and shineth even unto the west; so shall also the coming of the Son of man be." {DA 631.1}
The Saviour gives signs of His coming, and more than this, He fixes the time when the first of these signs shall appear: "Immediately after the tribulation of those days shall the sun be darkened, and the moon shall not give her light, and the stars shall fall from heaven, and the powers of the heavens shall be shaken: and then shall appear the sign of the Son of man in heaven: and then shall all the tribes of the earth mourn, and they shall see the Son of man coming in the clouds of heaven with power and great glory. And He shall send His angels with a great sound of a trumpet, and they shall gather together His elect from the four winds, from one end of heaven to the other." {DA 631.2}
At the close of the great papal persecution, Christ declared, the sun should be darkened, and the moon should not give her light. Next, the stars should fall from heaven. And He says, "Learn a parable of the fig tree; When his branch is yet tender, and putteth forth leaves, ye know that summer is nigh: so likewise ye, when ye shall see all these things, know that He is near, even at the doors." Matt. 24:32, 33, margin. {DA 632.1}Notice that Jesus passed over the events of that time by just saying that there would be great tribulation.
Then does not always have to indicate a progression of time, as in "after that". It could also indicate "at that time" - what ever time is being discussed in the verse.
Revelation 11:7 also supports this where it says
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 persecution of the church did not continue throughout the entire period of the 1260 years. God in mercy to his people cut short the time of their fiery trial. In foretelling the "great tribulation" to befall the church, the Saviour said, "Except those days should be shortened, there should no flesh be saved; but for the elect's sake those days shall be shortened." [MATT. 24:22.] Through the influence of the Reformation, the persecution was brought to an end prior to 1798. {GC 267}So, based on the Desire of Ages and the Great Controversy, verses 23 - 29 happen after 1798. And the Great Tribulation referred to here in Matthew 24:21 and 22 has already taken place.