Theliturgical reforms of Pope Pius XII took place mostly between 1947 and 1958.

On 20 November 1947,Pius XII issued the encyclicalMediator Dei. It included the statement: "the use of the mother tongue in connection with several of the rites may be of much advantage to the people", while reaffirming the normativity ofLatin.
Pius XII changed the requirements forfasting before receiving communion in two stages. In 1953, by theapostolic constitutionChristus Dominus, he continued to require not ingesting from midnight before receivingcommunion, but ruled that water did not break the fast. He also relaxed the fasting requirement for the sick and travelers, those engaged in exhausting physical labor, andpriests who celebrate several Masses on the same day. In 1957, withSacram Communionem, he replaced the fast from midnight with a three-hour fast from solid food and alcohol and a one-hour fast from other liquids. Ordinarycommunicants would calculate the time until the moment they took communion; priests fasted based on the time they began saying Mass.[1] The new fasting rules opened the way to scheduling evening Masses, which the fast from midnight regime made all but impossible for those desiring to receive communion.[2]
Permission for the use of thevernacular for parts of the Mass had been granted on occasion long before the papacy ofPius XII; including in 1906 byPius X (parts of Yugoslavia),Benedict XV in 1920 (Croatian, Slovenian, and Czech),Pius XI in 1929 (Bavaria).[3]
UnderPius XII, theSacred Congregation of Rites granted permission for the use of local languages in countries with expanding Catholic mission activities, including in Indonesia and Japan in 1941–2. In 1949 permission was granted for using Mandarin Chinese in Mass except for theCanon, and for the use of Hindi in India in 1950. Permission was also granted to use a French (1948) and German (1951) translation for rituals other than Mass.[3]
As a means of increasing the participation of the congregation in the celebration of Mass, recognizing that joining in chant is not possible at a Mass that is "read" rather than sung, in 1958 Pius approved the use of hymns in the vernacular at appropriate points in the service.[4] As a means to closer awareness by the congregation he also allowed the epistle and gospel to be read aloud by a layman while the celebrant read them quietly in Latin.[5]
Though insisting on the primacy of Latin in the liturgy of the Western Church (cf.Mediator Dei, par. 60), Pius XII approves the use of the vernacular in the Ritual for sacraments and other rites outside the Mass. All such permissions, however, were to be granted by the Holy See, and Pius XII strongly condemned the efforts of individual priests and communities to introduce the vernacular on their own authority. He allowed the use of the vernacular in other rites and sacraments outside the Mass,[6] in the service for Baptism andExtreme Unction.[7]
Following in the footsteps of his predecessors, Pius XII instituted a number of new feasts and approved newpropers. After defining theDogma of the Assumption in 1950, a new mass formula (the massSignum magnum) was introduced for the feast, which falls on August 15.[8] Pius XII also instituted thefeast of the Immaculate Heart of Mary, which he established as a double of the second class and fixed to August 22, the octave day of the Assumption.[9] Other new feasts included thefeast of the Queenship of Mary (May 31) and thefeast of Saint Joseph the Worker (to coincide with the socialist holiday of May 1), which thus replaced the Feast of Saint Joseph Patron of the Universal Church, observed until then (from 1870) as a movable feast on the third Wednesday after Easter.
TheSacred Congregation of Rites had jurisdiction over the Rites and ceremonies of theLatin Church such as Holy Mass, sacred functions and divine worship. It issued the location of the blessed sacrament within the Church, to be always at the main altar in the centre of the Church.[10] The Church should display religious objects, but not be overloaded with secondary items or evenKitsch. Modern sacredart should be reverential and still reflect the spirit of our time.[11] Since 1942, priests are permitted to officiatemarriages withoutHoly Mass.[12] They may also officiateconfirmations in certain instances.[13]
In 1951 on an experimental basis (ad experimentum),[14] and then permanently in 1956,[15] Pope Pius XII introduced theEaster Vigil, a celebration ofEaster night based on restoration of ancient forms.[16][14] He moved the time of the celebration to after sunset and restructured the service.[17] ThePaschal candle is the center of the service of new fire, rather than athree-branched candle of medieval origin which had existed only for use in this service; members of the congregation light their own candles as well, a participatory innovation. The water is blessed in front of the congregation, not at the baptismal font. Among many detailed changes, only four of the traditionalOld Testament readings were kept. Then followed only the first part of the Litany of the Saints and possible baptisms. A major innovation occurred with the incorporation of renewal of baptismal promises by the entire congregation, "a milestone" that introduced modern languages into the general Roman liturgy for the first time.[18]
His re-introduction of the Easter Vigil was generally popular, although it faced a cool reception from some prelates.Cardinal Spellman ofNew York considered asking for a dispensation from performing the new Easter Vigil rite,[19][20] but relented.[21] Another assessment saw initial enthusiasm that lasted only a few years and concluded that only novelty had attracted attention in the first years.[22] OtherChristian denominations adopted the popular Roman Catholic Easter ceremonies in later years, an ecumenical influence of Pius XII.[23]
In 1955, Pius XIIpromulgated new liturgies forHoly Week in the decreeMaxima Redemptionis (November 19, 1955). In addition to the new Easter Vigil, modified on an experimental basis in 1951 and now made permanent, he promulgated the rites forPalm Sunday,Holy Thursday andGood Friday, the most important ceremonies in the Roman liturgy. The Holy ThursdayMass of the Lord's Supper was moved from morning to evening to replicate more closely the experience of thehistorical Last Supper and the Good Friday liturgy similarly moved to the afternoon.[24]
The new Good Friday liturgy modified theGood Friday prayer for the Jews in two ways. Pius had already, in 1949, made a public declaration that the Latin word "perfidus", which is applied to the Jewish people in this prayer, means "unbelieving", not "perfidious" or "treacherous".[25] The 1955 liturgy rendered the text in English as "the faithless Jews". It also called for the congregation to kneel for a moment of silent prayer during this petition just as the congregation did during the other nine petitions in this liturgy.[26]
As theLiturgical Movement had long been exploring the history and form ofconcelebrating Mass, in 1956, Pius specified that all celebrants say the words of consecration aloud if they mean to participate fully, not just externally.[27]