On May 13, 1917, the Blessed Virgin Mary began appearing to three young children just outside the Portuguese village of Fatima. She would appear six times on the 13th of each month from May to October. The final apparition included the Miracle of the Sun. Thousands who were gathered saw the sun spin and seem to fall out of the sky, hurtling toward the earth, and then stop, and return to its place.

World War I was going on at that time, and Mary prophesied that that great war would soon end, but that if the world did not repent and turn back to God, another, even worse, war would break out. She spoke of the harm that would come to the world because of the sins of Russia. This was before the Communist revolution in Russia had taken place.
    
Of all of the apparitions of Mary, beginning with Our Lady of Guadalupe, and including those apparitions taking place in Medjugorje, her appearance as Our Lady of Fatima is the most important, and the others all seem to relate to her appearance in Fatima. 
    
This Tuesday, May 13, is the Feast of Our Lady of Fatima.

In the Acts of the Apostles, we are told, that after Jesus had ascended to the Father, the Apostles decided that it was important to choose someone to fill the role of Judas Iscariot, restoring the Twelve to their full number. It was decided that it should be someone who had been with them from the time of the Baptism of John. Lots were cast, and they chose a man named Matthias to fill that role.
    
The feast of St. Matthias is Wednesday, May 14