The unexpected coming of the Son of Man, 12:40: This imagery, drawn from Daniel 7:13 (although without “the clouds of heaven”), is usually understood to describe Christ’s coming to earth in the last day, although from Daniel’s perspective, the coming is from earth to heaven, a coming into the throne-room of the Ancient of Days where the Son of Man receives dominion, authority and power – a coming into God’s sanctuary in Zion. This coming images the day of judgment.
There have been many “comings” (divine acts of judgment, eg., Sodom and Gomorrah), and all prefigure the final “coming” of the Son of Man. In the Synoptic gospels, the destruction of Jerusalem in 70AD (one of the more significant comings of the Lord) serves as a paradigm for the final day of judgment. Given the eschatological nature of this final “coming” and its now / not yet enigma, observing the signs and calculating the day, is fraught, since the “coming” is at “an unexpected hour.”
As far as the now is concerned, Jesus is already on his throne, judgment complete, the “wedding feast” underway, but then in the terms of the not yet, Jesus has yet to close up the Monopoly-board of life; we still await the divine announcement, “Sorry boys and girls, the game is over!” So we are in a kind of Dr. Who moment, floating in the Matrix, or more properly, encapsulated in a moment of divine grace. To this end, a disciple must “be dressed for action”, persevering in faith, prepared for the coming “hour”.