The Vigil of St. Matthias, the Apostle

sotd thumbnailCommemoration is made, in the Mass of St. Peter Damian, of the vigil or eve of St. Matthias, Apostle, whose feast is kept on February 24, except in leap year; at that time it is kept on February 25.
This vigil was instituted by St. Pius V in order to raise the feast of St. Matthias to the same dignity as that of the feast of the other apostles.
(Source: Fr. Lasance, The New Roman Missal)