I think it simply means this KJ.
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:30 And then shall appear the sign of the Son of man in heaven: and then shall all the tribes of the earth mourn, and they shall see the Son of man coming in the clouds of heaven with power and great glory.
Then here means something happening in sequence, but if a thousand years = a day, what if we say this:
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:30 And then, two/three days later, shall appear the sign of the Son of man in heaven: and then shall all the tribes of the earth mourn, and they shall see the Son of man coming in the clouds of heaven with power and great glory.
All Jesus is saying is one thing follows the other, but no sense of the duration involved is given, but Peter clarifies this for us. As the 2nd Coming could literally happen at any time, it is simply sequential; Peter just clues us into the fact that actually it might not be as immediate as people hope or expect.
Same thing in Acts 2:19-20
Acts 2:19-20
And I will shew wonders in heaven above, and signs in the earth beneath; blood, and fire, and vapour of smoke: [20] The sun shall be turned into darkness, and the moon into blood, before that great and notable day of the Lord come:
Jerusalem will be burned to a frazzle before the return of the Lord. Will it happen a day before, a week before, five hundred years before, five thousand years before?
No one knows, because no-one knows when the Lord will return.