Earlier, I have argued that the two witnesses will minister in the first half of the Tribulation (assuming correspondence between the time periods of 3½ years in Revelation and Daniel).
The Great Tribulation is a short period of "never before seen" distress and persecution of God’s people living on the earth. The term "great tribulation" is used in a few translations of Matt. 24:21 (ESV, NASB and KJV) where Jesus said,
"For then there will be great tribulation,
such as has not been from the beginning of the world until now,
no, and never will be." (ESV)
It is normally attributed to the second half (3½ years) of the seven-year Tribulation though Scripture is silent on its duration. In the Olivet Discourse, Jesus went on to say in Matt. 24:22,
"If those days had not been cut short,
no one would survive,
but for the sake of the elect those days will be shortened." (NIV)
Would 3½ years of distress and intense persecution be considered short?
In Matt. 24:15-21, Jesus revealed that this period of great tribulation will take place when you see "the abomination that causes desolation" standing in the holy place as spoken by the prophet Daniel.
"He will confirm a covenant with many for one ‘seven.’
In the middle of the ‘seven’ he will put an end to sacrifice and offering.
And at the temple he will set up an abomination that causes desolation,
until the end that is decreed is poured out on him.” Dan. 9:27, NIV
According to Dan. 9:27, a future prince/ruler will make a covenant with many for seven years. However, in the middle of the seven years i.e., after 3½ years, he will put an end to sacrifices and offerings. And he will set up an abomination that causes desolation till his fate that has been decreed by God is finally poured out on him
Will this ruler appear in the temple when he stopped the sacrifices? If so, then he may be that abomination of desolation standing in the holy place. Others have taken the abomination of desolation to refer to the image of the beast from the sea that the false prophet would set up for all to worship (Rev. 13:13-15 cf., 2 Thess. 2:4). The image may be set up on "the wing of abomination" referring possibly to the highest point of the temple (see ESV translation of Dan.9:27 below).
"And he shall make a strong covenant with many for one week,
and for half of the week he shall put an end to sacrifice and offering.
And on the wing of abominations shall come one who makes desolate,
until the decreed end is poured out on the desolator.” Dan. 9:27, ESV
This action of the ruler standing in the holy place or of the setting up of the image of the beast in the temple would desecrate the temple. This desecration would then start from the middle of the seven years till the end of the rule of the beast. But this seems to conflict with Rev. 11:1-2 where the temple would be measured and this would presuppose that it had NOT be given to the Gentiles to be trampled upon; in other words, the temple would not be desecrated at this point in time. And if this argument stands then the abomination of desolation could NOT be standing in the temple in the middle of the Tribulation. If not then, when?
The seventh trumpet sounded the end of the kingdom of the world and the beginning of the kingdom of Christ (Rev. 11:15). In other words, the seventh trumpet would herald the dismantling of the beast's rule. Now, the beast would rule for 42 months (Rev. 13:5) so the seventh trumpet (aka the seven bowls) have to be sounded at the end of his rule i.e., at the end of the second half of the Tribulation ... thereby going beyond the seven-year Tribulation.
The following bowl judgments would be targeted specifically at the kingdom of the beast: (a) Bowl #1 on those with the mark of the beast and (b) Bowl #5 on the throne of the beast
Apart from these two, the followers of the Lamb would probably be afflicted by the other bowl judgments because we are not told otherwise; not that God cannot discriminate in His judgments (Exo. 9:23-26; 10:22-23). Also see "Tribulation Underwent by the Countless Multitude" discussed earlier. Remember, Jesus' words in Matt. 24:22, "If those days had not been cut short, no one would survive, but for the sake of the elect those days will be shortened."
The Book of Daniel also revealed a period longer than 3½ years for the second half of the Tribulation. The angel said to Daniel,
"From the time that the daily sacrifice is abolished
and the abomination that causes desolation is set up,
there will be 1,290 days.
Blessed is the one
who waits for and reaches the end of the 1,335 days." Dan. 12:11-12
And FROM the time that the daily sacrifice is taken away UNTIL the abomination of desolation, there shall be a thousand two hundred and ninety (1290) days.
and FROM the time of the turning aside of the perpetual sacrifice, and TO the giving out of the desolating abomination, are days a thousand, two hundred, and ninety (1290).
If the above reading of Dan. 12:11 is correct, the abomination of desolation would be set up 1,290 days after the daily sacrifices were stopped. Then the Great Tribulation would begin ... 30 days after the second half of the seven years (1,290 minus 1,260).
Note: Many have interpreted the stopping of the daily sacrifices and the setting up of the abomination of desolation as simultaneous events but then there would be no end event stated. Also see my argument above on the conflict with Rev. 11:1-2.
... and since the abomination of desolation would be set up at the end of the 1,290 days according to (the above interpretation of) Dan. 12:11, then I like to suggest that the period of 45 days is the Great Tribulation.
Note then that the bowls judgment would be poured out in rapid succession over 75 days starting from the end of the second half of the seven years.
Here is a summary chart of the sequence of events for your consideration.