During Advent we celebrate what are sometimes referred to as the "three comings of Christ": the coming of Christ in Bethlehem, the coming of Christ in glory at the end of time, and the coming of Christ today in the sacraments and life of the Church.

The first coming of Christ remains the central event of human history.  All time is dated from the birth of Christ.  The centuries leading up to Christ's birth are numbered B.C.: before Christ.  This year is officially the 2014th year since the birth of Jesus.  Even from a purely human point of view, no figure approaches Jesus Christ in significance.  No figure has had such an impact on the whole course of human affairs.

The effects of Christ, and of Christianity in general, upon the world are incalculable.  Without Christ, the world would not be what it is in all its positive aspects. The world in which we live is by no means perfect, and it will not be so until all things are finally transfigured and perfected in Christ. But we should never underestimate the radical alteration of history that came about through the birth of Christ into the affairs of humankind.
Second, Christ will come in glory at the end of time (the “second coming”). The Advent scriptures and prayers draw our minds to the coming of Christ in glory. Indeed, all the way through Advent, the primary liturgical theme is of Christ’s return in glory. At the end of the ages, Christ will come again and the heavens and the earth will be united.
It is important that we understand correctly the meaning of the return of Christ in glory. The end of all things will not be a matter of Christ returning to a world from which he departed at the ascension, but the appearance of Christ who is hiddenly present in the world as the latter continues on its journey.  What we are awaiting in Advent is the full blossoming of God’s grace working itself out in human history. Christ’s return will be, by God's grace, the marriage of heaven and earth.
The third coming of Christ occurs in the present:  in the vital, living action of Christ today in the community of the Church and in the lives of Christian believers. Christ comes today in the gift of the holy Eucharist in which we are privileged to share, in the sacraments of Christian life, in the living wisdom of the Christian tradition,  in the vocations consecrated for each of us in baptism, in the magnificent service and charity of Christian individuals, communities, and institutions across the face of the earth.
Certainly the church and its people have had, and always will have, an ambiguous and imperfect history. (We need only remind ourselves of the horrendous sexual abuse crisis that has recently haunted the Church.) But what would the world be like if there were no more Christian believers, no more sacraments, no more charity in the name of Christ? What if Christianity were to disappear?  What if there were no more people like Blessed Mother Teresa of Calcutta? The world would become a very different place. We should never underestimate the power of Christianity in our own time.
These three comings of Christ are what we invoke during this holy season.  We call upon Christ's presence that we may know the effects of his historic birth; we await the saving power of Christ’s return in glory; and we look in faith to his sacramental presence now.