For you yourselves know well that the day of the Lord comes like a thief in the night.
"The day of the Lord" usually refers in Scripture to a time in history characterized by God’s working in the world in direct, dramatic ways. [Note: See ibid., p. 109.] It contrasts with the day of man in which affairs appear to be proceeding without divine intervention. The eschatological day of the Lord prophesied in the Old Testament begins with the Tribulation and continues through the Millennium (cf. Isaiah 13:9-11; Joel 2:28-32; Zephaniah 1:14-18; Zephaniah 3:14-15; et al.). It contains both judgment (in the Tribulation) and blessing (in the Millennium). People living on the earth when it begins (i.e., unbelievers, since Christians will be with the Lord in heaven immediately following the Rapture) will not expect it.