Jesus Himself gave the messages of Divine Mercy to St. Faustina in Poland, just before World War II.
The Lord gave St. Faustina special intentions for the days leading up to Divine Mercy Sunday, the Sunday after Easter, and made many promises for those who pray the Divine Mercy Chaplet and celebrate Divine Mercy Sunday with Confession and Communion, with the intention to receive His plentiful graces. See the PDF documents below for the Chaplet, the Novena, and the promises!