In 2 Peter 1:13-15, the apostle Peter tells his audience that the Lord had shown him the time of his death was near. Depending on the source, Peter died somewhere between 64 and 68 A.D.
The destruction of the temple which occurred in 70 A.D., was very close to the time of Peter’s death. Peter certainly would have known that the coming judgment on the temple and Jerusalem was very close.
According to the Olivet Discourse (Matthew 24,) Jesus gave his disciples an estimated time frame as when the destruction of the temple would occur. The aged apostle knew the destruction of the Temple was very soon to happen. Yet in contrast, Peter tells his audience the following regarding the Day of the Lord.
But, beloved, be not ignorant of this one thing, that ONE DAY is with the Lord AS A THOUSAND YEARS, and a thousand years as one day. ~ 2 Peter 3:8
Why would Peter say such a thing if he believed the coming destruction of the temple (which was very near) was emphatically the Day of the Lord he is describing in his epistle?
Conversely, Peter appeals to his audience to remain steadfast in the Lord knowing that God is not slack concerning his promise, but is patient towards us, not willing that any should perish, but that all should come to repentance.
A careful reading of Matthew 24:1-35 shows a stark contrast from that of 2 Peter 3. The message of the destruction of the temple was to “get -out” and flee from Jerusalem. The message in 2 Peter is that God waits patiently from men to come to repentance and we should live holy and godly lives because the Day of the Lord will catch the whole world by surprise.
The down fall of Jerusalem happened over the course of weeks, months, and years. The coming of the Day of God, to which Peter is referring, is going to come suddenly as a thief in the night.