The great St. Augustine of Hippo wrote a little about a lot of things and a lot about a few things. Being a late convert, someone who, let’s say, might have preferred that what happened in Hippo stayed in Hippo, he wrote incessantly about his struggles with sin and his constant need of conversion and repentance. That’s to say that he was a regular person in that regard, though regular people rarely write it all down. Augustine also wrote brilliantly about time, the theology of time, and yet his most famous quote about time is this: “What then is time? If no one asks me, I know; but if I wish to explain it to one who asks, I do not know.”
Time is a popular subject in the Bible It’s a one way street, though – people are always asking God about time. “How long will you hide your face from me?” (Psalm 13) “How long, LORD, must I call for help, but you do not listen?” (Hab 1) “‘Lord, is this the time when you will restore the kingdom to Israel?’” (Acts 1)
It’s seemingly constant. It’s the Biblical equivalent of having toddlers in the backseat of the car asking “Are we there yet?” It shows human beings to be impatient, grasping, ignorant, small creatures, like gnats buzzing around the ears of God. But it might also show humanity at its best.
We are all too aware that, as Paul Mills writes, “We are temporal creatures with a finite lifespan. Western lifestyle is dominated by considerations of time to such a degree that the clock is rivalled only by the printing press as the most influential invention of this millennium. In societies less obsessed with temporal flow, we are known as ‘people with gods on their wrists’. Time travel is a pervasive theme of our science fiction.
“Yet, with Augustine, although we instinctively know what time is and can sense its passing, we have extreme difficulty in defining it. We perceive time as approaching us from the ‘future’, passing across the vanishingly brief boundary of the ‘present’, into the ‘past’, but we cannot sense whether the past and the future exist as realities other than for their moment in the present.
“While some biblical writers depict history having cyclical features, the overriding picture is of time within this universe being linear, having both a beginning (at creation), and a definite end (e.g. Acts 17:30-1). We do not know the exact time of the end, but it is already known by the Father (Mark 13:32). History has a fixed end-point, and therefore a destination. This contrasts particularly with the Hindu notion that time is endlessly repetitive and cyclical, which can result in apathy about the consequences of our actions within time. Rather, the belief that time is linear encourages purposive action (Psalm 90:10, 12).” 
Said another way, “Take heed, watch; for you do not know when the time will come.” Jesus was with His disciples in Jerusalem when one of them admired the majesty of the Temple. “Do you see all these great buildings?” replied Jesus. “Not one stone here will be left on another; every one will be thrown down.” People being people, a few of Jesus’ disciples cornered Him and asked, “Tell us, when will these things happen?”
Jesus gives a long discourse about the signs and wonders that will proceed the end of days, everything from the Gospel being proclaimed to all peoples to persecutions to the stars falling from the sky, but then He says, “But about that day or hour no one knows, not even the angels in heaven, nor the Son, but only the Father.”
Jesus here sees humanity at its perhaps annoying best: the buzzing falls out of “When will this happen?”, and it sounds more like, “We love you and long for your return.” “Are we there yet?” sounds more like “Your absence from us is dreadful.”
“Take heed, watch; for you do not know when the time will come,” becomes less of a warning and more of a comfort: “I am coming,” says the Lord, and so stop worrying about when. Because ‘when’ becomes both a producer of anxiety and an easy out: a countdown clock both makes us buzz around like gnats and lets us ignore our duties to each other and to the Lord.
This Advent, take the time to mark the time, to notice its passing, to make use of the time our Lord gives us, and give Him thanks for not letting us know what time He’ll get back.