I am one of those who believes that the signs enumerated by the Lord in today's Gospel were given precisely to demonstrate the impossibility of calculating when He will return in glory to judge the living and the dead. Can you think of a time during your own life when the nations have not been in disarray, or when there have been no natural disasters, or predictions of cosmic catastrophies? I can't.
I think Christ's point is that He can return at any time, which is why He gave this exhortation:
Beware that your hearts do not become drowsy from carousing and drunkenness and the anxieties of daily life, and that day catch you by surprise like a trap. For that day will assault everyone who lives on the face of the earth. Be vigilant at all times and pray that you have the strength to escape the tribulations that are imminent and to stand before the Son of Man” (Luke 21:34-36)But even if the Lord does not return soon, you do not know when you will be called to meet Him. Does death not catch many unawares? This is why St Paul, in what is perhaps the very first pastoral letter he wrote, which would make it the earliest book of the New Testament, prays that the Lord will increase the abundance of love in and among the Christians of ancient Thessaloniki- so that they would conduct themselves in a manner pleasing to God in order to be found blameless and holy in His sight when Christ returns. The Lord's return has been imminent ever since His ascension.
Today we begin a new year of grace, a new time of preparation, another chance to turn our eyes from what is passing and ephemeral to what is eternal and real. We do this by letting ourselves be drawn more deeply into the Paschal mystery, the very core of reality, that is, into the birth, life, death, resurrection, and ascension of our Lord Jesus Christ, which is what the Eucharist is all about. As Fr Robert Hart noted, "to prepare for the coming again of Jesus Christ, we need do no more, and no less, than we do when we prepare to receive the Communion of His Body and Blood."
We begin each new liturgical year by putting last things first, or, stated another way, we begin by putting what matters most first. So, on this first Sunday of Advent we look forward to Christ's return in glory, which will usher what the prophet Jeremiah called "The LORD our justice."
Our collect for the First Sunday of Advent expresses all of this very well:
the resolve to run forth to meet your Christ
with righteous deeds at his coming,
so that, gathered at his right hand,
they may be worthy to possess the heavenly Kingdom.
Through our Lord Jesus Christ, your Son,
who lives and reigns with you in the unity of the Holy Spirit,
one God, for ever and ever.