Songs of thankfulness and praise, Jesus, Lord, to thee we raise. (Christopher Wordsworth [1807-1885])
Epiphany is both a Holy Day and a season. The Holy Day itself is on January 6 - concluding the twelve days of Christmas. The season then begins with Christ's baptism, and concludes with the Transfiguration. It's length varies, because the season fills the gap between the Day of Epiphany and the Season of Lent.
What you will notice about these two days, is that there are some striking similarities between them. At both Christ's Baptism, and His Transfiguration, we hear the voice of God the Father saying some very similar words. "This is my son, my beloved, with Him I am well pleased." The account of the Transfiguration contains the additional charge, "Listen to Him (Luke 9:35 NRSV)."
In "Soul Physicians" Robert Kellemen describes says this about the nature of the Trinity, "They were experiencing constant, uninterrupted, intimate, relationship. They were together, in harmony, giving, sharing, relating - loving (Soul Physicians pg 62)."
During the Season of Epiphany we get snapshots of this Trinitarian Love as it relates to Christ's ministry here on earth. "You are my Son, my beloved. With You I am well pleased." Ephiphany is designed to orient us to this divine love that is constantly being given and received - a love that has its root in the Trinity, is meant to encompass humanity, and all of the world by extension.
Having been reminded of our divine destiny in Advent, celebrating God with Us at Christmas, Epiphany is the logical extension. Here we celebrate how the divine nature, specifically the divine love, is becoming an integral part of our world.