Vigils are divided into two classes, major and minor; major vigils are the vigils of Christmas, Epiphany and Pentecost, and they are called privileged vigils and are celebrated as semi-doubles. The vigils of Christmas and Pentecost are privileged vigils of the first class. The vigil of Epiphany is a privileged vigil of the second class. All others are minor or non-privileged vigils.
Etymology and nature. The word “octave” is from the Latin octavus (eighth) because, in the early ages of Christianity, the Church celebrated the eighth day only after the celebration of the feast itself; not until the twelfth century was the custom of a commemoration on each of the eight days introduced. We have, probably, an example of this still in our Breviaries. The feast of St. Agnes is celebrated on 21st January and on 28th it is mentioned at Vespers and Lauds only, and the name in old Roman service books is Octavo, S. Agnetis. The origin of the octave is Jewish. We read in the Old Testament that God ordered that the Feasts of Pasch and Pentecost should be celebrated for eight days. So, too, the Feast of Tabernacles lasted for eight days, the first and eighth days being days of special celebration and devotion. The Christian Church adopted the method of showing great honour and glory to the principal festivals of the Christian year, to the great saints, the patrons of countries, dioceses, etc. But just as the calendar became overcrowded with saints’ offices, which excluded almost entirely the Sunday and ferial offices, so, too, the additions of octaves created confusion and further tended to the exclusion of the old liturgical use of the Psalter and the supplanting of the Sunday and ferial offices. Hence, in the Motu Proprio Abhinc duos annos, the octaves of the calendar are divided into three great classes, privileged, common and simple. Privileged octaves are further divided into three orders. Those of the first order are the octaves of Easter and Pentecost; the octaves of Epiphany and Corpus Christi belong to the second order, and the octaves of the Nativity and Ascension belong to the third. The Christmas octave admits feasts of saints, but the octaves of Epiphany, Easter and Pentecost do not admit any feasts (Tit. V., sec, 3). A day within an octave has a right to first Vespers, and the antiphon and response should be from first Vespers (S.C.R., June, 1905). But the feast of the day falling within octave has a right to first and second Vespers. The exceptions are, when at second Vespers of St. Thomas, the office of the octave of the Nativity to be observed on 30th December has to be commemorated again, in octaves like octaves of Epiphany when each day has its proper antiphon at the Magnificat, and again on and July in second Vespers of Visitation the office of St. Peter and Paul is to be commemorated. In octaves the suffrages of saints and the Athanasian Creed are not said. When feasts of the Universal Church, which are celebrated with an octave are perpetually transferred to the next day, because of a perpetual impediment, according to the rubrics, the octave day is not therefore perpetually transferred but ought to be kept as in the Universal Church on its own day.