On February 23rd the Church commemorates the Vigil of St. Matthias, whose feastday is kept tomorrow on the 24th day of February. In a leap year, the Vigil of St. Matthias is kept on February 24, and any Feasts usually occurring from February 24 through 28 are kept one day later. Because February 23rd is the Feast of St. Peter Damian, this Vigil is only commemorated in the Church's liturgy when it falls on February 23rd.
While not one of the original twelve apostles, St. Matthias is honored with the same rank of as the other Apostles as he legitimately took the spot which the traitor Judas Iscariot lost. This election is recounted in detail in the Acts 1:12-26. The Holy Ghost would not have inspired so many lines about his election were it not important.
Before the changes to the Roman calendar in 1955, nearly all feasts of the Apostles were preceded by a special Vigil Day. And the Church put those days in place to help us prepare for the importance of a feast of an Apostle. We have lost the importance of the feasts of the Apostles I believe, in part, due to losing the vigils. We can change that for ourselves by observing these vigils in our own prayer lives.
Collect:
Grant, we beseech Thee, almighty God, that the solemn feast of Thine apostle Matthias, which we anticipate, may both increase our devotion and advance our salvation.
Prayer by Dom Gueranger to St. Matthias:
O Apostle Mathias! thou didst complete the sacred college, from which Judas had fallen; and by the power of the Holy Ghost, thou didst put to flight the darkness of idolatry by the admirable lightnings of thy wise words. Do thou now beseech the Lord that he grant peace and much mercy to our souls. Amen.