Tenebrae (Latin for ‘shadows’ or ‘darkness’) is a Christian religious service celebrated by the Western Church on the eves of Maundy Thursday, Good Friday, and Holy Saturday, which are the last three days of Holy Week. The liturgy of Tenebrae is characterized by the gradual extinguishing of candles while a series of readings and psalms are chanted or recited. In the Roman Rite of the Roman Catholic Church the Tenebrae readings and psalms are those of Matins and Lauds, brought forward to the preceding evening. In 1955 Pope Pius XII decreed an end of this practice, making an exception only for cathedrals that celebrate the Mass of the Chrism in the morning of Holy Thursday, which he allowed to continue to bring Matins and Lauds of that day forward to Wednesday evening. Since then, Tenebrae is no longer widely celebrated in the Roman Catholic Church, even on the Wednesday evening. Some churches within the Anglican Communion also celebrate Tenebrae. The name may also be used for various Holy Week services among Protestant churches (Wikipedia).