The "Day of the Lord" talk in this verse is certainly apocalyptic. There are a lot of different takes on this verse, but the kernel we need to keep our eyes on is consistent: God will judge the world, and God will purify the world. The world was his, always has been, and always will be. If we are obedient and following our Saviour, the Day of the Lord will be a reason for rejoicing, because we are people of the Lord.