Endtimes, Millennium, Rapture
The term "endtimes" applies both to the era of Christ's first coming (Heb 1:2, 1 Cor 10:11, Heb 9:26) and to the events immediately before his return and the end of the ages (Mt 24:13, 2 Tim 2:1, 2 Peter 3:3). The definitive Catholic teaching on the endtimes is contained in the Catechism of the Catholic Church under the discussion of the article of the Creed, "From thence He will come again to judge the living and the dead." [CCC 668-682]
As the Creed infallibly teaches, the Second Coming is associated with the end of the world and the Last Judgment. Therefore, it is NOT associated with any earlier time - such as to establish a "Millennium." The Catholic Church specifically condemns "millenarianism," according to which Jesus will establish a throne in this world and reign here for a thousand years [CCC 676]. She teaches instead that Jesus already reigns in eternity (1 Cor. 15:24-27, Rev. 4 & 5) and that in this world His reign, established as a seed, is found already in the Church [CCC 668-669]. This is the 1000 years, which is the Hebrew way of indicating an indefinite long time - in this case, the time between the first and second comings, the era of the Church, in other words the last days in the broadest sense.The Book of Revelation situates this era between the persecutions of the Roman antichrists of the first century and the final unleashing of evil at the end.
Naturally, non-Catholics cannot accept that the Catholic Church represents Christ in this world, so they are forced to look for a personal earthly reign somewhere out in the future. The notion that Jesus will come, reign, and then depart, so that the devil can trick the world again, is incompatible with the incomprehensible dignity of the Lord and His love for His people. Jesus' Coming will be definitive, triumphant and ever-lasting, NOT temporal and limited.
As for the Rapture, the meaning of 1 Thes 4:15-17 is that at the return of Christ (v.15) and the General Resurrection of the Dead (v.16), those who survive the persecution of the Antichrist will have no advantage in being resurrected over those who died before His Coming [CCC 1001]. All will go to meet Him and be with Him forever (v.17; cf. Rev 20:17-21:27).
The Catechism provides us with a general order of events at the End [CCC 673-677]. Chronologically they are,
1. the full number of the Gentiles come into the Church
2. the "full inclusion of the Jews in the Messiah's salvation, in the wake of the full number of the Gentiles" (#2 will follow quickly on, in the wake of, #1)
3. a final trial of the Church "in the form of a religious deception offering men an apparent solution to their problems at the price of apostasy from the truth." The supreme deception is that of the Antichrist.
4. Christ's victory over this final unleashing of evil through a cosmic upheaval of this passing world and the Last Judgment.
As Cardinal Ratzinger recently pointed out (in the context of the message of Fátima), we are not at the end of the world. In fact, the Second Coming (understood as the physical return of Christ) cannot occur until the full number of the Gentiles are converted, followed by "all Israel."
Approved Catholic mystics (Venerables, Blessed and Saints, approved apparitions) throw considerable light on this order, by prophesying a minor apostasy and tribulation toward the end of the world, after which will occur the reunion of Christians. Only later will the entire world fall away from Christ (the great apostasy) and the personal Antichrist arise and the Tribulation of the End occur.
Although this is not Catholic doctrine, arising as it does from private revelation, it conforms to what is occurring in our time, especially in light of Our Lady of Fátima's promise of an "Era of Peace." This "Triumph of the Immaculate Heart" (other saints have spoken of a social reign of Jesus Christ when Jesus will reign in the hearts of men) would seem to occur prior to the rise of the Antichrist. The optimism of the Pope for the "New Evangelization" and a "Civilization of Love" in the Third Millennium of Christianity fits here, as well. This would place us, therefore, in the period just before the events spoken of in the Catechism, that is, on the verge of the evangelization of the entire world. Other interpretations are possible, but none seem to fit the facts as well, especially when approved mystics are studied, instead of merely alleged ones.