It is celebrated on September 14 of each year.
In 326 AD Saint Helen went to Jerusalem to worship the Holy Land and thank God for the triumphs of her son Constantine the Great. The Divine zeal, however, made Saint Helen to begin research to find the Holy Cross.
On Golgotha there was a pagan temple of the goddess Aphrodite, which he tore down and began the excavations. At one point, three crosses were found. The excitement was great, but which of the three was the Lord’s? Then the bishop of Jerusalem Makarios with several priests, after praying, touched the body of a pious lady who had died on the crosses. When her turn came and she touched the third cross, which was really the Lord’s, the woman immediately rose again.
The news spread like lightning to all parts of Jerusalem. Crowds of devotees began to flock to touch the holy wood. However, because many accidents occurred due to the overcrowding, they raised the Holy Cross inside the temple to a high place, so that everyone could see it and worship it.
So, this elevation was established by the holy Fathers, to be celebrated on September 14th, so that we too could raise in our souls the Cross of our Lord, which was par excellence a “weapon against the devil”.
Some Synaxarists, on this day, also mention the elevation of the Holy Cross in Constantinople in 628 AD. by King Heraclius, who had defeated and retaken the Holy Cross from the Avars, who had seized it from the Holy Land.