David, the great tribulation begins when the AoD is setup - not 30 days later.
David, where you are going wrong is mentally adding "great" in front of "tribulation of those days". The tribulation of those days is the 1290 days of the 1335 day long great tribulation.
What verse has "1260 days" in the text that you are locking everything into?
Why would that be wrong? What other tribulation is mentioned in Matthew 24 prior to that of verse 29 if not meaning great tribulation? I don't see a mention of great tribulation then being followed by a different tribulation prior to that of verse 29. I know some Amils see that being the case, except you are not an Amil. It is plainly obvious that the trib of those days have to be involving great tribulation.
Matthew 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.
Matthew 24:29 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:
Why would it be unreasonable to think that 'those days' pertaining to verse 29 are pertaining to 'those' days pertaining to verse 22? Are you going to argue that 'those days' pertaining to verse 22 are not involving tribulation? And does not the 'those days' recorded in verse 29 pertain to tribulation as well?
Daniel 12:7 And I heard the man clothed in linen, which was upon the waters of the river, when he held up his right hand and his left hand unto heaven, and sware by him that liveth for ever that it shall be for a time, times, and an half; and when he shall have accomplished to scatter the power of the holy people, all these things shall be finished.
a time, times, and an half---this equals great tribulation, it equals 1260 days. If we compare to Revelation 10, this is what that ch records.
Revelation 10:6 And sware by him that liveth for ever and ever, who created heaven, and the things that therein are, and the earth, and the things that therein are, and the sea, and the things which are therein, that there should be time no longer:
7 But in the days of the voice of the seventh angel, when he shall begin to sound, the mystery of God should be finished, as he hath declared to his servants the prophets.
Notice that it says in the days rather than day, of the voice of the seventh angel. Which means at the beginning of the 7th trumpet we are no longer in this 1260 day period. We are now in the beginning of the 6th seal events, which then involve the final 7 vials of wrath, then at the end of that once the 7th trumpet is sounding for the last time, keeping in mind, that if it is involving days, the 7th trumpet can sound multiple times, both at the beginning of it and at the ending of the 7th trumpet events. And then when it sounds for the last time we are now in the time during/after the 7th vial, thus the 2nd coming of Christ and the rapture of the church. Thus the mystery of God is now finished.
These 45 days are then involving the days of the 7th trumpet leading up to the 2nd coming at the end of these 7th trumpet events. After all, since both the 6th seal and the 7th trumpet involve the wrath of God, it is then not unreasonable to place the 6th seal events during the time of the 7th trumpet, then at the end of these days involving the 7th trumpet, the 2nd coming and the rapture of the church occurs. Which then tends to make sense out of Revelation 16:15 and why that is in the text where it is, between the 6th and 7th vial. Because it is telling us, as of the 6th vial, Christ hasn't returned at this point.
Some interpreters tend to think, that at the beginning of the 7th trumpet is when the 2nd coming occurs. Except that is not the only option since it could be at the end of the 7th trumpet events that the 2nd coming occurs. It's still during the 7th trumpet no matter how you look at it. And if the 7th trumpet is involving the 7 vials of wrath, by making the 2nd coming at the end of the 7th trumpet rather than at the beginning of it at least doesn't have repenting still being an option after Christ has returned.
Revelation 16:9 And men were scorched with great heat, and blasphemed the name of God, which hath power over these plagues: and they repented not to give him glory.
Assuming this is during the 7th trumpet, which makes more sense in that case, this is meaning after Christ has already bodily returned? Or before Christ has bodily returned? OTOH, if this is not even involving the days of the 7th trumpet, in that case that makes my point moot altogether. But if it is involving the days of the 7th trumpet, there you go then.