Exaltation of the Holy Cross
Roodmas 1 — more commonly known simply as “Holy Cross Day” — was first begun to commemorate the Dedication of the Basilica of the Resurrection, built by St. Helena (Constantine the Great’s mother), in Jerusalem in A.D. 355 — but the true Cross was found shortly thereafter, also by St. Helena, so the two events were joined.
The story of the finding of the True Cross, from the Catholic Encyclopedia:
In the year 326 the mother of Constantine, Helena, then about 80 years old, having journeyed to Jerusalem, undertook to rid the Holy Sepulchre of the mound of earth heaped upon and around it, and to destroy the pagan buildings that profaned its site. Some revelations which she had received gave her confidence that she would discover the Saviour’s Tomb and His Cross. The work was carried on diligently, with the co-operation of St. Macarius, bishop of the city.
The Jews had hidden the Cross in a ditch or well, and covered it over with stones, so that the faithful might not come and venerate it. Only a chosen few among the Jews knew the exact spot where it had been hidden, and one of them, named Judas, touched by Divine inspiration, pointed it out to the excavators, for which act he was highly praised by St. Helena. Judas afterwards became a Christian saint, and is honoured under the name of Cyriacus.
During the excavation three crosses were found, but because the titulus was detached from the Cross of Christ, there was no means of identifying it. Following an inspiration from on high, Macarius caused the three crosses to be carried, one after the other, to the bedside of a worthy woman who was at the point of death. The touch of the other two was of no avail; but on touching that upon which Christ had died the woman got suddenly well again.