<P> During the 3rd century and 4th century, in addition to the celebration of Mass, it was customary to hold a vigil, which was a prayer service in three parts, on the night before a feast day . Vigils, in a strict sense, were night - watches in preparation for the feast . Commenced in the evening, they terminated only the following morning, and involved, in addition to the eucharistic supper, homilies, chants, and divers offices . </P> <P> The Office of the Vigils was a single Office, recited without interruption at midnight . The number of psalms, which at first varied, was subsequently fixed at twelve, with the addition of a lesson from the Old Testament and another from the New Testament . From this vigil service developed three of the canonical hours: Vespers, Matins, and Lauds, inasmuch as the first was prayed the preceding evening, and the last was held in the early hours of the morning . This was the arrangement already in the days of Hippolytus († 236). St. Benedict of Nursia, in his description of the liturgy of the hours, always refers to vigils as the night office . After the vigil service had split into Vespers, Matins, and Lauds, Matins became three divisions known as nightwatches or nocturns . </P> <P> A Roman Catholic Mass that counts liturgically for a Sunday or Holy Day but which takes place the previous evening is often mistakenly called a Vigil Mass . But it is more accurately termed an "anticipated Mass," because a Vigil is actually the whole day prior to certain major feasts, which acts as sort of Western version of the forefeast . And such Vigils (such as Christmas Eve) have their own proper Mass theoretically said that morning . </P>

What is a vigil mass at catholic church