The Proper of the Day: Feast of the Holy Cross

Today the Church celebrates the Feast of the Holy Cross (transferred from yesterday because it falls on a Sunday this year). This festival grew out of the fact that the Cross, the central symbol of Christianity since the 2nd century, is "celebrated" on Good Friday, when Our Lord was crucifed on one. But that day is not really a joyous occasion, when in fact the Cross itself is ultimately a wonderful thing. So the idea of a seperate celebration that focuses on the Exaltation of the Cross as opposed to its Pain took hold. This is similar to why we observe the Feast of Corpus Christi - Maundy Thursday itself, which is the institution of the Eucharist, is the day before Good Friday and not in and of itself a joyful time.

As to how the date of September 14 came to be, here's what Lesser Feasts and Fasts has to say:

The historian Eusebius, in his Life of Constantine, tells how that
emperor ordered the erection of a complex of buildings in Jerusalem “on
a scale of imperial magnificence,” to set forth as “an object of attraction
and veneration to all, the blessed place of our Savior’s resurrection.” The
overall supervision of the work — on the site where the Church of the
Holy Sepulchre now stands — was entrusted to Constantine’s mother,
the empress Helena.

In Jesus’ time, the hill of Calvary had stood outside the city; but when
the Roman city which succeeded Jerusalem, Aelia Capitolina, was built,
the hill was buried under tons of fill. It was during the excavations
directed by Helena that a relic, believed to be that of the true cross, was
discovered.

Constantine’s shrine included two principal buildings: a large basilica,
used for the Liturgy of the Word, and a circular church, known as “The
Resurrection” — its Altar placed on the site of the tomb — which was
used for the Liturgy of the Table, and for the singing of the Daily Office.
Toward one side of the courtyard which separated the two buildings, and
through which the faithful had to pass on their way from Word to
Sacrament, the exposed top of Calvary’s hill was visible. It was there that
the solemn veneration of the cross took place on Good Friday; and it
was there that the congregation gathered daily for a final prayer and
dismissal after Vespers.

The dedication of the buildings was completed on September 14, 335,
the seventh month of the Roman calendar, a date suggested by the
account of the dedication of Solomon’s temple in the same city, in the
seventh month of the Jewish Calendar, hundreds of years before
(2 Chronicles 7:8-10).

Here's a haunting setting of the anthem Adoramus Te, Christe, "We Adore You, O Christ":

Almighty God, whose Son our Savior Jesus Christ was lifted high upon the cross that he might draw the whole world to himself: Mercifully grant that we, who glory in the mystery of our redemption, may have grace to take up our cross and follow him; who lives and reigns with you and the Holy Spirit, one God, in glory everlasting. Amen.

RFSJ