From Fransiscan Media:
Between May 13 and October 13, 1917, three Portuguese children–Francisco and Jacinta Marto and their cousin Lucia dos Santos–received apparitions of Our Lady at Cova da Iria near Fatima, a city 110 miles north of Lisbon. Mary asked the children to pray the rosary for world peace, for the end of World War I, for sinners, and for the conversion of Russia
Mary gave the children three secrets. Following the deaths of Francisco and Jacinta in 1919 and 1920 respectively, Lucia revealed the first secret in 1927. It concerned devotion to the Immaculate Heart of Mary. The second secret was a vision of hell. When Lucia grew up she became a Carmelite nun and died in 2005 at the age of 97.
Pope John Paul II directed the Holy See’s Secretary of State to reveal the third secret in 2000; it spoke of a “bishop in white” who was shot by a group of soldiers who fired bullets and arrows into him. Many people linked this vision to the assassination attempt against Pope John Paul II in St. Peter’s Square on May 13, 1981.
The feast of Our Lady of Fatima was approved by the local bishop in 1930; it was added to the Church’s worldwide calendar in 2002.