I believe the Rev 12 ‘short time’ applies to the period since the resurrection. 12 Therefore rejoice, ye heavens, and ye that dwell in them. Woe to the inhabiters of the earth and of the sea! for the devil is come down unto you, having great wrath, because he knoweth that he hath but a short time. Revelation 12 KJV The timing is clear because Satan is cast out by the blood of the Lamb: 10 And I heard a loud voice saying in heaven, Now is come salvation, and strength, and the kingdom of our God, and the power of his Christ: for the accuser of our brethren is cast down, which accused them before our God day and night. 11 And they overcame him by the blood of the Lamb, and by the word of their testimony; and they loved not their lives unto the death. The duration must be more than 1,260 years since this is the time the woman is nourished in the wilderness: 13 And when the dragon saw that he was cast unto the earth, he persecuted the woman which brought forth the man child. 14 And to the woman were given two wings of a great eagle, that she might fly into the wilderness, into her place, where she is nourished for a time, and times, and half a time, from the face of the serpent. Revelation 12 KJV This is also the short time referred to by Jesus: 16 A little while, and ye shall not see me: and again, a little while, and ye shall see me, because I go to the Father. John 16 KJV Satan was cast out of heaven after his judgement: 7 Nevertheless I tell you the truth; It is expedient for you that I go away: for if I go not away, the Comforter will not come unto you; but if I depart, I will send him unto you. 8 And when he is come, he will reprove the world of sin, and of righteousness, and of judgment: 9 Of sin, because they believe not on me; 10 Of righteousness, because I go to my Father, and ye see me no more; 11 Of judgment, because the prince of this world is judged. John 16 KJV I think the Rev 20 period comes after the thousand year earthly rule of Jesus and represents the final appeals to judgment before sentence is carried out.