The term “octave” derives from the Latin word for “eighth” (in music, the eighth note). Octave has two meanings in Catholic liturgical use: either the eighth day after a feast, when reckoned inclusively, or the whole period of these eight days. Initially, the octava dies was associated with the weekly celebration of Christ’s resurrection every eighth day, which would be Sunday. The practice of other liturgical octaves was first introduced in the fourth century.
Among the divisions in the Liturgical Year, marked in their descending significance, you find: Solemnities, feasts, and memorials. Easter and the days that follow are all solemnities. According to the Universal Norms of the Liturgical Year & Calendar, “Solemnities are counted among the most important days, whose celebration begins with First Vespers (Evening Prayer I) on the preceding day. Some Solemnities are also endowed with their own Vigil Mass, which is to be used on the evening of the preceding day, if an evening Mass is celebrated. The celebration of the two greatest Solemnities, Easter and the Nativity, is extended over eight days. Each Octave is governed by its own rules” (UNLYC, nn. 11-12). Thus, as an eight-day period, whether following Easter or Christmas, the octave continues to be celebrated as if they were the actual feast. The final eighth day is also called the octave or “octave day,” and those days in between its first and last day are said to be “within the octave.” Thus, the first eight days after Easter celebrate the Solemnity of Easter each and every day and, then, the octave ends on the Second Sunday of Easter or Divine Mercy Sunday.
Starting from at least the 3rd or 4th century, the Church began this liturgical practice in order to extend certain feasts beyond the initial day of their observance. This meant that the joyous celebration of Easter Sunday is prolonged from one day to eight full days. In fact, the practice developed to treat each day in the octave as if it were Easter Sunday. This tradition has been preserved by the Roman Rite and many of the Eastern Rites, where the liturgical readings and actions of each day mimic what took place on Easter Sunday.
For the newly baptized, the Easter Octave once had a different significance. During those eight days, those formerly known as the Elect are now called neophytes. As newly initiated into the faith, they would wear their baptismal gowns during the entire octave. Around the fourth century of the Christian era, in order to serve as catechesis for the newly baptized about the divine mysteries that they had just experienced on Easter, in the Diocese of Rome, each of those days the neophytes attended Mass at a different church, at which they received Holy Communion. Then, in the evening, wearing their white baptismal garments, they went to Saint John Lateran, the Cathedral Church of Rome, for the Office of Vespers or Evening Prayer. On the last or eighth day of the Octave—today known as the Second Sunday of Easter—that day came to be identified in Latin as dominica in albis [deponendis] or, in English, the Sunday of the (laying aside of the) white garments.
In an Easter homily, the late Pope Benedict XVI underscored that tradition and in regard to the final or eighth day of the octave, he explained, “This Sunday concludes the Octave of Easter. It is a unique day “made by the Lord”, distinguished by the outstanding event of the Resurrection and the joy of the disciples at seeing Jesus. From antiquity this Sunday has been called “in albis” from the Latin word alba (white) because of the white vestments the neophytes put on at their baptism on Easter night and set aside eight days later” (Castel Gandolfo. Midday Regina Caeli. 11 April 2010).
Saint Augustine sensitive to the dangers faced by the newly baptized, cautioned the neophytes, “These Festival Days are now at an end, and the days that follow are given over to daily meetings, demands, disputes. Be careful, brethren, how you pass your life amid these things. From the quiet life of these past days you should take in gentleness of spirit.”
Nature and dignity 