During the days of the Arian controversy, when a Christian Bishop named Arius was contending that Jesus was not to be properly understood as an actual full son of God, but rather one who was elevated to such a position from a lower form of existence and given great insight from Heaven, there was an interesting manifestation in the skies above Jerusalem. It was generally taken to refute Arianism. 

  Arianism held that Jesus was something less than the Son of God.  But who besides God could place Jesus's well known sign (the cross) in the sky above what God called His Holy Mountain (Mt. Zion).

  The Bishop of the Christian Church in Jerusalem then was a man named Cyril, (b. approx 315 A.D. - d. approx 386 A.D.) who was not an Arien adherant, but essentially what came to be called a 'trinity' believer. The manifestation ocurred on May 7th, 351 A.D.

  It occurred early in Cyril's Episcopate (time as Bishop) on the 'nones of May' just after Pentecost. At about 9:00 A.M. a large cross appeared in the sky, stretching roughly from Golgotha, the attested sight of Jesus's crucifixion, to the Mt. of Olives just east of the city of Jerusalem, so it was pretty large. This distance should approach 1/2 mile, if I remember correctly from visiting there. It was described as being 'brighter than the sun'. It's significant that 9:00 A.M. was about when Jesus's crucifixion had begun approx. 319 years earlier, or perhaps 320 years earlier. This manifestation lasted for several hours, so it was by no means brief. It was reported as visible to all in the city of Jerusalem.

  The Christians living in Jerusalem then hurried to church to praise God and no doubt to talk excitedly about this. We've all heard of miracles, but to see one all together with your fellow believers would certainly have been a faith strengthening event. I know I'd love to have been there, though I believe anyway.

  Praise God, who never quits trying to reach and strengthen believers.