Epiphany is on January 6th.
In the West, this festival focuses on the worship of the Magi, the Epiphany of the Christ to the Gentiles. Thus many missions hymns are Epiphany hymns and vice versa. (So much for the need for World mission sundays or evangelism sundays. Just follow the church year and you will find everything you need, sooner or later.)
In the East however, Epiphany focuses on the baptism of Christ. The Epiphany is of the Holy Trinity at the Jordan. The Father speaks, the Son receives baptism, and the Spirit descends. In the East, the day has a rich mix of Christological, Trinitarian and sacramental themes apparent in many of the Eastern father's sermons for Epiphany.
Here is a short section of Gregory of Nyssa's sermon "On the Baptism of Christ".
Christ, then, was born as it were a few days ago--He Whose generation was before all things, sensible and intellectual. To-day He is baptized by John that He might cleanse him who was defiled, that He might bring the Spirit from above, and exalt man to heaven, that he who had fallen might be raised up and he who had cast him down might be put to shame.
And marvel not if God showed so great earnestness in our cause: for it was with care on the part of him who did us wrong that the plot was laid against us; it is with forethought on the part of our Maker that we are saved. And he, that evil charmer, framing his new device of sin against our race, drew along his serpent train, a disguise worthy of his own intent, entering in his impurity into what was like himself,--dwelling, earthly and mundane as he was in will, in that creeping thing.
But Christ, the repairer of his evil-doing, assumes manhood in its fulness, and saves man, and becomes the type and figure of us all, to sanctify the first-fruits of every action, and leave to His servants no doubt in their zeal for the tradition.
Baptism, then, is a purification from sins, a remission of trespasses, a cause of renovation and regeneration. By regeneration, understand regeneration conceived in thought, not discerned by bodily sight. For we shall not, according to the Jew Nicodemus and his somewhat dull intelligence, change the old man into a child, nor shall we form anew him who is wrinkled and gray-headed to tenderness and youth, if we bring back the man again into his mother's womb: but we do bring back, by royal grace, him who bears the scars of sin, and has grown old in evil habits, to the innocence of the babe. For as the child new-born is free from accusations and from penalties, so too the child of regeneration has nothing for which to answer, being released by royal bounty from accountability.
And this gift it is not the water that bestows (for in that case it were a thing more exalted than all creation), but the command of God, and the visitation of the Spirit that comes sacramentally to set us free. But water serves to express the cleansing. For since we are wont by washing in water to render our body clean when it is soiled by dirt or mud, we therefore apply it also in the sacramental action, and display the spiritual brightness by that which is subject to our senses.