In Vilnius, Jesus spoke to st. Faustina:

"Write this down: Before I come as the just Judge, I shall come first as the King of mercy. Before the day of justice comes, humankind will be given this sign in the sky."

"All the light in the sky will be extinguished, and there will be great darkness all over the Earth. Then the sign of the cross will appear in the sky, and great light shall come down from the holes where the Saviour's hands and feet were pierced, and shall illuminate the Earth for a time. This will happen a short time before the last day."

(St. Faustina’s diary, no 83, p. 45)