If you would like some more detail of the history of the Proclamation head over to New Liturgical Movement.
Although calendars now give the date of Easter and the other feasts in the liturgical year for many years in advance, the Epiphany Proclamation still has value. it is a reminder of the centrality of the resurrection of the Lord in the liturgical year and the importance of the great mysteries of faith which are celebrated each year. This beautiful proclamation puts everything into perspective. Every liturgical celebration of the Church finds its authentic meaning in the Paschal Mystery, even Christmas. The Paschal Mystery was precisely why the Eternal Son of the Father, the Eternal Word, deigned to leap down from heaven and become incarnate in the womb of the Blessed Virgin Mary. He was born in time so that He could give His flesh for the life of the world.
Below is the Proclamation with the dates for 2013 as per the Irish Liturgical Calendar.
the glory of the Lord has shone upon us,
and shall ever be manifest among us,
until the day of his return.