The "Day of the Lord" is the day when He returns for His people, which comes upon them as a "thief in the night" and will be "as it was in the days of Noah...when the Flood came and took them all away".
The destruction of the Antediluvians happened in one day - violent torrential rains fell everywhere, the singular landmass of the Earth broke apart as subterranean forces exploded forth and shot massive columns of huge rocks and superheated water upward (one inspired writer says Satan was compelled to remain in the midst of the destruction which was so severe, he feared for his very existence), and since the high mountain ranges didn't exist then, but are actually the result of this destruction, there's no way humanity could have survived for more than a day from this incredibly lethal judgment of God.
Yep, still missing the whole point of the Day of the Lord.
Actually it took 40 days:
"And the flood was forty days upon the earth; and the waters increased, and bare up the ark, and it was lift up above the earth."
"And the waters prevailed upon the earth an hundred and fifty days."
Just to make sure, the ark was left above the waters for another 150 days.
How about 2 Peter 3? Genesis 2?
Are you saying that no one survives the 6th Seal event, to live on earth for the rest of the judgments? Who is on earth when the 7th Seal is opened? Who is on earth when the Trumpets sound?
If you claim one continent was broken up into what we have today, and the mountains were formed in one day, what does the 6th Seal do in seconds?
"And I beheld when he had opened the sixth seal, and, lo, there was a great earthquake; and the sun became black as sackcloth of hair, and the moon became as blood; And the stars of heaven fell unto the earth, even as a fig tree casteth her untimely figs, when she is shaken of a mighty wind. And the heaven departed as a scroll when it is rolled together; and every mountain and island were moved out of their places."
You don't think God could put all the continents back into a single continent, and remove the mountains into smaller "hills" in a few seconds? While not killing a single human?
Yet you accept a human explanation over the 40 days it took to lift the ark up to the tops of the known "hills"? In a judgment that was supposed to kill every last human on earth, accept those in the ark.
The point of the Second Coming and subsequent Day of the Lord is not to kill off all the wicked. In fact it is to give them a chance to keep repenting, even if they don't ever repent. In one of the Trumpets, they want to die, and may even try, but cannot. The point is to remove souls from Adam's dead corruptible flesh.
None of that changes the fact, that the 6th Seal is the surprise, thief in the night moment, when all are claiming peace and safety, and in seconds they have a totally different earth as a single continent, and everything thing they hold dear has been burned up. Not a drawn out Flood of water. No verse says it is going to take 24 hours for the 6th Seal to happen. That is not what the phrase Day of the Lord means.
The point is not to cause chaos, yet the state of mind will be chaotic on that day. The point is to restore the earth to the way God intended it to be.
"For the great day of his wrath is come; and who shall be able to stand?"
That wrath won't be over in 24 hours either. The great day of His wrath is not the same phrase as the Day of the Lord. And neither means 24 hours. Both "days" come with a lot of quick and sudden destruction. Both "days" play out totally different in meaning. Both "days" come when least expected. But the wrath part has to be accomplished before the Day of the Lord can start.
Case in point. When Moses led Israel out of Egypt the Day of deliverance started with a rejection. They were not out of Egypt and in the promised land in 24 hours. In fact after 40 years, not many including Moses even arrived, who started the journey. Probably only Joshua and Caleb.
The Day of the Lord comes. But there is a process of wrath before it can start, and few will make it through to the "promised land". Those last ones only get there by having their heads chopped off as a testimony to Jesus Christ.