The story of the Seven Sleepers of Ephesus was already well known by the 6th century and their feast day was celebrated by Western and Eastern Church. The miracle was first described by Bishop Stephen of Ephesus (448-451). St. Gregory of Tours also wrote about it, and The Golden Legend of Jacobus de Voragine made it known throughout the Middle Ages.
Because of the verifiability of the incident and its immediate popularity around the world, the historicity of the Seven Sleepers of Ephesus was never doubted until the 16th century. It was the rise of Protestantism and, after that, the Enlightenment that put doubts about the Seven Sleepers, and it began to be called apocryphal and a legend.
For those who trust the good original sources mentioned, the long sleep of the seven youth is a miracle that God made to show the truth of the resurrection of the body. Their story follows.