Saints festivals are listed in the Calendar of the Catholic Church. This is called the General Roman Calendar. This is issued from Rome, and the last major revision was in 1969, when St Christopher and other saints had their feast days removed from the world-wide calendar.
At the issue of the 1969 Calendar, 30th of May was listed as a feria. "Feria" is a Latin word that, in church usage, means "weekday"; more precisely, it refers in the calendar to days on which no saint is celebrated.
In the earlier Calendars of 1954 and 1962, 30th of May is listed as the Feast of Pope Felix I, Martyr. A Roman by birth, Felix was chosen as Pope on 5 January 269, in succession to Pope Dionysius, who had died on 26 December 268.
The acts of the Council of Ephesus give Pope Felix as a martyr; but this detail, which occurs again in the biography of the pope in the "Liber Pontificalis", is unsupported by any authentic earlier evidence and is manifestly due to a confusion of names. In in the Roman dating system. Saint Felix I is mentioned as Pope and Martyr, with a simple feast, on 30 May.
In the USA American Catholic Website lists Saint Gregory VII as Saint of the Day for 30 May.
The tenth century and the first half of the eleventh were dark days for the Church, partly because the papacy was the pawn of various Roman families. In 1049, things began to change when Pope Leo IX, a reformer, was elected. He brought a young monk named Hildebrand to Rome as his counsellor and special representative on important missions. He was to become Gregory VII.
Image: Wax funeral effigy of Gregory VII under glass, Salerno cathedral
Three evils plagued the Church then: simony (the buying and selling of sacred offices and things), the unlawful marriage of the clergy and lay investiture (kings and nobles controlling the appointment of Church officials). To all of these Hildebrand directed his reformer’s attention, first as counselor to the popes and later (1073-1085) as pope himself.
Pope Saint Gregory VII (c. 1015/1028 – May 25, 1085), born Hildebrand of Sovana (Italian: Ildebrando di Soana), was Pope from April 22, 1073, until his death. One of the great reforming popes, he is perhaps best known for the part he played in the Investiture Controversy, his dispute with Henry IV, Holy Roman Emperor affirming the primacy of the papal authority and the new canon law governing the election of the pope by the college of cardinals. He was at the forefront of both evolutionary developments in the relationship between the Emperor and the papacy during the years before becoming pope. He was beatified by Gregory XIII in 1584, and canonized in 1728 by Benedict XIII as Pope St. Gregory VII.