The Feast of the Apparition of the Holy Cross commemorates a miraculous event that graced the skies of Jerusalem. On May 19, 351, a magnificent radiant cross, shining with celestial light, appeared over the city, spanning from the Mount of Olives to Golgotha and visible to all who looked toward the heavens.
Bishop Kyuregh (Cyril) of Jerusalem wrote a letter to Emperor Constantius II about this miraculous event, interpreting the shining cross as a heavenly sign affirming the protection of the Orthodox faith against Arianism. He urged the emperor to cease his support for the Arians.
He urged the emperor to withdraw his support for the Arians and uphold the doctrine of the Church. This sacred letter, preserved in an Armenian translation, is solemnly read in the Armenian Apostolic Church on the feast day.
The Armenian Apostolic Church observes this feast on the Sunday of the fourth week after Easter, which falls between April 19 and May 23, in remembrance of the celestial sign that once illuminated the holy city.