DIVINE MERCY CHAPLET

The Chaplet of the Divine Mercy, also called the Divine Mercy Chaplet, is a Christian devotion to the Divine Mercy, based on the Christological apparitions of Jesus reported by Saint Faustina Kowalska, known as "the Apostle of Mercy." What makes this prayer so powerful is that we are offering Christ Himself to God the Father; and nothing has such power as the offering of Jesus of Himself to His Father and ours. And so, the Chaplet of Divine Mercy is very much about the conversion, sanctification and salvation of souls - primarily those approaching death.
Faustina wrote that Jesus promised that all who recite this chaplet at the hour of death or in the presence of the dying will receive great mercy. ... According to Roman Catholic tradition, the chaplet may be said at any time, but it is said especially on Divine Mercy Sunday and Fridays at 3:00 PM.