10 But the day of the Lord shall come as a thief, in which the heavens shall pass away with great violence, and the elements shall be melted with heat, and the earth and the works which are in it, shall be burnt up. 11 Seeing then that all these things are to be dissolved, what manner of people ought you to be in holy conversation and godliness? 12 Looking for and hasting unto the coming of the day of the Lord, by which the heavens being on fire shall be dissolved, and the elements shall melt with the burning heat? 13 But we look for new heavens and a new earth according to his promises, in which justice dwelleth.
Haydock Commentary (by Fr. Robert Witham, 1667–1738)
Ver. 10.The heavens, &c. He puts the faithful in mind not to regard these profane scoffers, but to be convinced of the truths revealed, and that the world shall be destroyed a second time by fire. Reflect that the time of this life, and all the time that this world shall last, is nothing to eternity, which has no parts, no beginning, nor end; so that in the sight of God, who is eternal, a thousand years are no more to be regarded than one day, or one moment. The long time that hath hitherto passed, must not make you think that God is slack as to his promises, or that they shall not infallibly come to pass at the time and moment appointed by his divine providence. God’s infinite mercy, and his love for mankind, bears patiently with the provocations of blind and unthinking sinners, not willing that any of them should perish, but that they should return to him by a sincere repentance and true penance, and be saved. But watch always, according to the repeated admonition of our blessed Redeemer. Mark xiii. 37. &c. For both the day of your death, and the day of the Lord to judge the world, will come like a thief, &c. Wi.
Ver. 11.Seeing then that all these things are to be dissolved, that the world, and all things in the world, shall pass in a short time, set not your affections upon them: let your life and conversation be holy. According to the divine promises, look for new heavens, and a new earth, where justice is to dwell, whither sinners shall not enter, but the just only, in a new state of never-ending happiness. Make it then your endeavour to be found in the sight of God spotless and blameless; and look upon the long forbearance of God, who defers to punish sinners as they deserve, to be an effect of his mercy, and for your salvation. Wi.
The term Day of the Lord has different meanings depending on the context in which it is used. There will be a final Day of the Lord, however, since this term almost always implies judgement from God, there have been different events where this term was used.
Throughout Israel’s history there have been events in which judgment and destruction has befallen them for their idolatry and wickedness. In Scripture we often read different variations of “in that day”, or “on that day,” or “the day is fast approaching” etc etc. When Day is used in these contexts, they are ultimately thought of as the Day of the Lord. Which basically means judgement.
So there have been multiple judgements in Salvation history and in the end there will be one final judgment. Or in other words, there have been multiple Days of the Lord and there will be one final Day of the Lord.