General Roman Calendar of 1954

In 1954, Pope Pius XII (1939–1958) made changes to the General Roman Calendar, incorporating the same calendar established by Pope Pius X (1903–1914) following his liturgical reforms, as well as changes that were made by Pope Pius XI (1922–1939), such as the institution of the Feast of Christ the King (assigned to the last Sunday in October). Some of Pope Pius the XII's changes include the institution of the Feast of the Immaculate Heart of Mary (August 22, which was previously the octave day of the Assumption of Mary) in 1944, the inscription of Pius X into the General Calendar (September 3) following his 1954 canonization, and the institution of the Feast of the Queenship of Mary (May 31) in October 1954.

Source: Wikipedia — General Roman Calendar of 1954 (CC BY-SA 4.0)