Modern scholars of the Navigatio focus less on exploration and more on symbolism. While the text regularly provides details about sailing times, for example, the numbers are often suspiciously Biblical: short journeys last three days, longer ones last forty days, and the whole expedition takes seven years. A medieval reader would have been reminded of the three persons of the Trinity and the three days from Good Friday to Easter; of the forty days that Jesus fasted in the desert and the forty days of fasting at Lent and other times in the year; and of the seven days in which God created the world and the seven religious services constituting the Divine Office (on which see below). The entire journey, indeed, can be read as an extended metaphor. Brendan and his monks are on a quest: they journey on the sea of life, through fogs of uncertainty, on a boat offering the protection of the Church, to a promised land of salvation.

Central to the narrative are two religious cycles, an annual one and a daily one, each of which was crucial to Christians of the time and to the spiritual message of the Navigatio. The annual liturgical calendar is at the heart of the story: instead of a linear journey of exploration—in which the travelers actually get somewhere interesting, like America—the monks of the Navigatio travel in circles, celebrating the most important Christian celebrations in the same places each year, for seven years in all. Four holy days are identified (by a talking bird) as the central ones (14.32): three celebrations connected with Easter and Christmas.

In the Navigatio, Easter observances begin on Maundy Thursday (also called Holy Thursday); this is the commemoration of the Last Supper (the final dinner of Jesus and the disciples) and thus of the Eucharist (also called the Mass and Holy Communion). Brendan and his monks celebrate Maundy Thursday on the “Island of Sheep.” They remain there the next day, which modern Christians know as Good Friday (the day on which Christ was crucified), and the first part of Holy Saturday (the day before Easter Sunday, commemorating the resting of Christ in the tomb). They are there for a symbolic “three days” (11.39; 15.9). Curiously for a modern Christian, Good Friday is not mentioned explicitly; the focus is instead on Maundy Thursday and thus on the Last Supper.

Later, on Holy Saturday, the monks move to what they think is a nearby island, but (spoiler alert) is really a whale. They stay there until Easter morning. This episode brings to mind the most famous whale in the Bible, the one that swallowed Jonah, an event interpreted by Christians as a symbol of Christ’s death and resurrection. On Easter afternoon the travelers move to a third island, the “Island of Birds,” and remain there till the week after Pentecost.Pentecost takes place fifty days after Easter; it is also called Whitsunday and celebrates the descent of the Holy Spirit described in the Book of Acts; it is technically the most important Christian holy day after Easter). The islands (really two islands and a whale) thus constitute a trinity, symbolic not only of the Holy Trinity itself but also of the three days between the crucifixion of Jesus (on Good Friday), his time in Hell, and his Resurrection (on Easter Sunday).

Christmas is celebrated every year on the Island of Ailbe, far distant from the islands of the Easter observances.  Other Holy Days are also mentioned:

Advent, the preparation for Christmas; there are four Advent Sundays before Christmas, and the first Sunday in Advent marks the beginning of the Ecclesiastical year.

Epiphany on January 6 in the Western church, celebrating the presentation of Christ to the Magi, and thus to the Gentiles more generally.

The Purification of the Virgin Mary on February 2 (also known as Candlemas), celebrating her successful delivery of the infant Jesus.

The Feast of St. Peter and St. Paul on June 29. Our text refers only to St. Peter, who as a former fisherman was particularly important to travelers on the sea.

The Assumption of the Virgin Mary on August 15 in the Western church, celebrating Mary’s bodily ascent to heaven at the end of her earthly life.

Though far from a full liturgical calendar, these references perhaps invite the reader to infer that Brendan and his monks observed the complete religious calendar for each year of their voyage..

The other cycle important to the Navigatio is the daily round of prayer services, traditionally seven in all, that was at the center of monastic life, in addition to Mass / Holy Communion. This cycle has various names, such as “the liturgy of the hours,” “the canonical hours,” “the hours,” “the daily office,” “the divine office,” and “the work of God” (opus Dei). The origins and development of the cycle are disputed, and neither modern nor ancient practice has ever been uniform. Identifying specific times is complicated by the fact that the times for dawn and sunset are variable, but the following is a rough guide for modern practice in western churches.

Matins (like “satins”) / Mattins /Night office Midnight or 2.00 AMMatins can be combined with Lauds (like “bawds”).
Prime First hour (of daylight), 6.00 AM
Terce (like “hearse” or “pierce”) Third hour, 9.00 AM
Sext Sixth hour, 12.00 PM
None (like “phone”) / Nones  Ninth hour, 3.00 PM
Vespers (like “testers”) Evening, before sunset
Compline (like “hotline” or “poplin”)   Bedtime

The Navigatio offers three separate accounts of the Daily Office. The most complete is in chapter 17. The travelers land on the “Island of Strong Men” (or “Island of Three Choirs”) after Terce, but the implied daily schedule is as follows:

ad vigilias matutinas  Matins  / Night office Midnight or 2.00 AM
cum dies illucessisset  Prime 6.00 AM
ad tertiam Terce Third hour, 9.00 AM
sexta Sext Sixth hour, 12.00 PM
ad horam nonam None / Nones Ninth hour, 3.00 PM
ad vesperas Vespers Evening, before sunset

Compline is omitted, which would have struck most readers as surprising. In chapter 11, on the “Island of Birds,” they celebrate Easter as follows:

usque ad tertiam vigiliam noctis Matins  / Night office Midnight or 2.00 AM
cum aurora refulsisset Prime 6.00 AM
ad tertiam horam  Terce Third hour, 9.00 AM
ad sextam Sext Sixth hour, 12.00 PM
ad nonam None / Nones Ninth hour, 3.00 PM
vespertina hora Vespers Evening, before sunset

Again, there is no mention of Compline. In chapter 12, on the “Island of Ailbe,” there is no detailed list of services, though both Vespers and Compline are mentioned (12.40; 12.49).

For many modern readers, it is easy to dismiss both cycles of religious observance as mere background to the broader narrative. But in a text probably composed by a monk, perhaps mainly for other monks, the liturgical hours are central. As Patricia Rumsey puts it, “For mediaeval monks the liturgical year was a microcosm of the whole mystery of salvation. As the feasts and fasts of the yearly cycle unfolded they represented all the significant moments in the life of Christ and swept the worshippers into their pageantry and ritual so that they too could share by faith in these sacred events.”