The period from January 6th until the day before Ash Wednesday.
The origin of the feast of the Epiphany lies in the Eastern celebration of the incarnation, and its fundamental concern is the epiphany, or theophany, the manifestation, the revelation of God to the world in Jesus Christ.
The date for this feast in the East is 6 January, possibly because this was the original date of the winter solstice in the East, possibly too because it was the
pagan festival of the birth of a god. Certainly, as with Christmas in the West, this was the Christianizing of an existing celebration.
It seems clear from the evidence that originally the Eastern epiphany on 6 January celebrated two things, the birth of Christ (all aspects of it including the visit of the magi), and the baptism of Jesus, and that this remained the case until the late fourth century. Evidence that this was so in Egypt in the period 380-400 comes from John Cassian’s Conferences, and up to 385 in Antioch from a sermon preached there by John Chrysostom at Whitsun 386, where he makes reference to the Epiphany as the first of the Christmas festivals, commemorating the appearance of God on earth. But by 380 sermons preached by Gregory of Nazianzus in Constantinople make it clear that Christmas was being celebrated there on 25 December. No doubt this was a copying of the Western celebration of Christmas on that date, by then established for half a century or so, and this spread rapidly all over the East in the last quarter of the fourth century. So the incarnation was detached from the baptism in liturgical celebration, with all aspects of the former, including the visit of the magi, being celebrated on 25 December, leaving the original united feast of the Epiphany to commemorate subsequently only the baptism Christ.
However when the borrowing took place in the other direction, and the West acquired a feast of the Epiphany on 6 January, it did not adopt the Eastern commemoration of the baptism. Instead it separated a part of the Christmas story off for celebration on that date, namely the visit of the magi, and this has been what the West has celebrated at Epiphany since.
Nevertheless, in the modern West, the celebration of Christmas Day now totally overshadows 6 January, and Christmas itself is in practice a united feast covering all aspects of the stories surrounding birth of Jesus including the visit of the magi. In contrast, the Eastern theme of the baptism of Jesus has never been prominent in the West until very recent times. But the traditional Western sequence of gospel readings at the eucharist for the Sundays after the Epiphany is a series of passages that may be said to demonstrate the manifestation of God in Christ, the first two in the series being the story of Christ’s visit to the temple in Jerusalem as a boy of twelve years of age and the miracle of turning water into wine at the marriage at Cana in Galilee.
In the liturgical revisions towards the end of the last century the West has built the theme of the baptism of Jesus into its Epiphanytide celebrations in the choice of gospels provided for the first Sunday after the Epiphany, in the modern Roman rite, in the proposals of the Joint Liturgical Group, in service books of churches that have largely adopted these proposals, including the British Methodist and United Reformed Churches, and in modern Anglican revisions including those of Australia, England and the USA. Thus perhaps it may be said that in this respect the West has finally caught up with the East after a gap of 1600 years. In these modern revisions subsequent Sundays appoint a variety of gospel passages that continue the Epiphany theme in a broad way, as did the traditional series of Epiphanytide Western Sunday gospels.