There is an ancient tradition, dating back at least as far as the fifth century, of announcing the date of Easter (and of other festivals whose date depends on Easter) at Epiphany.
Christians in a number of churches (and notably in some Anglican churches) have revived this old tradition in recent decades. Why announce the date of Easter at Epiphany? – Because at Epiphany we recall that the Magi brought to the infant Jesus gifts of myrrh, gold and frankincense. These gifts teach us that Jesus came to die to for us, that death could not hold him, and that he lives to intercede for us at the right hand of the Father. In other words, the Epiphany point us towards Good Friday, Easter Day, and Ascension Day.
When this announcement is made in church, it is sung to the Exsultet chant.
Here is the announcement for 2021:
Know, dear 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 Saviour.
On the 17th day of February will fall Ash Wednesday, and the beginning of the fast of the holy Lenten season.
On the 4th day of April we shall celebrate with joy Easter Day, the Paschal feast of our Lord Jesus Christ.
On the 13th day of May will be the Ascension of our Lord Jesus Christ.
On the 23rd day of May, the feast of Pentecost.
On the 28th day of November, the First Sunday of the Advent of our Lord Jesus Christ, to whom is honour and glory for ever and ever. Amen.