PROCLAMATION OF FEASTS – One of the special traditions connected with Epiphany was the publication on January 6 of the annual letter of the patriarch of Alexandria announcing the date of Easter for the current year (epistola festalis). The scholars of Alexandria were considered most competent to make the difficult computations and observations necessary to determine this date, and thus the whole East followed their findings, which were sent to all churches by the patriarch. In the sixth century, the fourth Council of Orleans (541) ordered the same procedure in the West. During the Middle Ages the dates of other movable feasts observed in the Church were directed to be added to the date of Easter and all of them to be solemnly read to the people on Epiphany Day. This ancient custom is still observed in some cathedrals as a traditional solemnity on January 6 at the end of Pontifical Mass.
THE MOVABLE FEASTS are Easter, whose date depends on the paschal moon, and those other feasts whose date depends on that of Easter.
The Roman Pontifical describes the solemn announcement (publication) of the movable feasts on the Twelfth Day of Christmas (The Feast of the Epiphany):
On Epiphany, the Gospel being sung, the archdeacon or a canon, prebendary, or another ecclesiastical dignitary according to local custom, vested in a cope shall ascend the ambo (pulpit) and there, or in some other place where the Gospel customarily is sung) shall by the time-hallowed establishment of Holy Mother Church announce the movable feasts of the current year according to the form here below written:
KNOW YE, best-beloved brethren, that by the consent of God's mercy,
as we have rejoiced for the Birth of our Lord Jesus Christ,
so also we declare to you joy for the Rising of the same our Saviour.
The (day, month) will be the Sunday at Septuagesima.
The (day, month) will be Ash Wednesday, and the beginning of the fast of Lent most hallowed.
The (day, month) you shall celebrate with joy Holy Easter of our Lord Jesus Christ.
The (day, month) will be the Ascension of our Lord Jesus Christ.
The (day, month) will be the feast of Whitsunday.
The (day, month) will be the feast of the most hallowed Corpus Christi.
The (day, month) will be the first Sunday of the Advent of our Lord Jesus Christ,
to whom is honor and glory, for ever and ever. Amen.
The Pontifical also provides for the announcement of the diocesan synod at this ceremony.