On the bowls, my view is that they occur within the 42 months of the reign of the beast, see Revelation 13:5. The beast is only given 42 months [second-half]. The bowls depict the beast still having a throne, a kingdom, followers, the ability to wage war, etc. Therefore the bowls are within the scope of that 42 months, but within the scope of the wrath of God, see Revelation 15:1, 14:19, and within the scope of the Day of the LORD. (Source)
I want to comment on this.
1. When the Antichrist’s authority of 42 months (3 1/2 years) expires, the Antichrist is not simply going to raise the white flag and hand over his kingdom to Christ’s newly-proclaimed kingdom. Antichrist is going to fight it out, even though his divinely-given authority over a kingdom has expired. Just as Antichrist will execute military operations before his 42 months of special authority, he will do so after his 42 months. To say that he can before but cannot afterwards is inconsistent. So Antichrist can operate outside of his special authority of 42 months. Before the 42 months he prepares his rule, after the 42 months he tries to persist in his rule.
At the completion of the seven-year period, the seventh trumpet is blown with the pronouncement that the kingdom of the world has now (officially) become the kingdom of the Lord. However, the enemies of God are not going to roll over; thus, the first act of King Jesus is to wipe out his opponent through the bowl judgments culminating in Armageddon—it will be a matter of procedure for King Jesus to clean up.
So after Antichrist’s authority of 42 months expires, he will attempt (unsuccessfully) to keep his authority, kingdom, and followers by waging war against Christ. Just as Satan’s special authority was defeated at the cross, Satan is still at war against God and his people.
2. There are good exegetical reasons that show that the sixth trumpet completes the seven-year period, and the seven trumpet is blown soon after, which introduces the bowl judgments. As a preface, the references to three and one-half years in the books of Daniel and Revelation refer to the latter half of the seven-year period (e.g., Time, times and half of time: Dan 7:25; 12:7; Rev 12:14; 1260 days: Rev 12:6; forty-two months: Rev 11:2; 12:5; Rev 13:5). Thus, it is very unlikely, though not impossible, Revelation 11:3 is the only instance referring to the first half. Further, Jesus and Paul use Daniel as an important source for their teachings, and the astute reader will observe they focus on the events happening during the second half, emphasizing the midpoint event: the revelation of Antichrist. Therefore, it is not probable the instance of three and one-half years in Revelation 11:3 refers to the first half of the seven-year period.
The implication to the previous conclusion is it places the prophetic ministry of the two witnesses in the final half, lasting 1,260 days (i.e., forty-two months or three and one-half years). They would be killed on the last day of the seven-year period (11:7), and after three and one-half days, they will be brought to life (11:11). Accordingly, the death of the two witnesses occurs between the sixth trumpet and the seventh trumpet. The second woe / sixth trumpet will be completed at the devastating earthquake in Jerusalem (11:13–14), happening after the three and one-half years ministry, death, and resurrection of the two witnesses (11:3–12). Therefore, the seventh trumpet / third woe only occurs after the seven-year period is completed (Rev 11:15). In other words, placing the ministry of the two witnesses during the first half cannot be exegetically maintained. For that would require the trumpet judgments to happen during the first half, which is not possible because they occur after the seventh seal, which in turn is opened sometime during the second half of the seven-year period.
3. The seventh trumpet pronounces Christ as king, which will be blown shortly after the completion of the mystery of the salvation of the remnant of Israel and the fullness of the Gentiles: “The kingdom of the world has become the kingdom of our Lord and of his Christ, and he will reign for ever and ever” (Rev 11:15). At that time, Christ establishes his rule in Jerusalem, followed by the final wrath in the bowl judgments including the battle at Armageddon.
The timing of this pronouncement of Christ reclaiming his kingdom has confused some interpreters because it occurs before the bowl judgments and Armageddon. Some interpreters resolve this “problem” by positing the pronouncement as a “preview” or “anticipation” of God’s rule on earth, denying its actualization at this point in time. However, there is no need to postulate a “preview” interpretation. Before the bowls are unleashed, the pronouncement of God’s rule on earth is the first event of the third woe / seventh trumpet: “(14) The second woe has come and gone; the third is coming quickly. (15) Then the seventh angel blew his trumpet” (Rev 11:14–15). Shortly after the conclusion of the seven-year period, God will reclaim his earthly kingdom at the blowing of the seventh trumpet. Then the key function of the bowls will authenticate God’s kingdom and the demise of Antichrist’s kingdom; therefore, they are instrumental in the final transitional phase replacing Antichrist’s rule with Christ’s rule.