On this day the Catholic Church remembers St. Faustina Kowalska, 1905-1938.
"Sister Mary Faustina, an apostle of the Divine Mercy, belongs today to the group of the most popular and well-known saints of the Church. Through her the Lord Jesus communicates to the world the great message of God's mercy and reveals the pattern of Christian perfection based on trust in God and on the attitude of mercy toward one's neighbors."
--from the Biography at the Vatican web site.
But not all Catholics find St. Faustina or her private revelations helpful or credible.