It was necessary to make known the date of Easter in advance, since many celebrations of the liturgical year depend on its date. The number of Sundays that follow Epiphany, the date of Ash Wednesday, and the number of Sundays that follow Pentecost are all computed in relation to Easter.
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.
On the Epiphany of the Lord, after the singing of the Gospel, a Deacon or cantor, in keeping with an ancient practice of Holy Church, announces from the ambo the moveable feasts of the current year according to the following text.
(video courtesy of Conception Abbey)
Announcement of Easter and the Moveable Feasts
(for the year 2014)
Know, dear brethren (brothers and sisters),
that, as we have rejoiced at the Nativity of our Lord Jesus Christ,
so by leave of God's mercy
we announce to you also the joy of his Resurrection,
who is our Savior.
and the beginning of the fast of the most sacred Lenten season.
On the twentieth day of April you will celebrate with joy Easter Day,
the Paschal feast of our Lord Jesus Christ.
[In those places where the Ascension is observed on Thursday:
On the twenty-ninth day of May will be the Ascension of our Lord Jesus Christ.]
[In those places where the Ascension is transferred to the Seventh Sunday of Easter:
On the first day of June will be the Ascension of our Lord Jesus Christ.]
On the eighth day of June, the feast of Pentecost.
On the twenty-second day of June, the feast of the Most Holy Body and Blood of Christ.
On the thirtieth day of November, the First Sunday of the Advent of our Lord Jesus Christ,
to whom is honor and glory for ever and ever.
(information courtesy of the United States Conference of Catholic Bishops, www.usccb.org )