Question: When did the place where the head of the catholic region named after the same saint as the Dakovo Cathedral become its own country?

Knowledge 1: Đakovo Cathedral
The Đakovo Cathedral or Cathedral basilica of St. Peter () is the cathedral of the Roman Catholic Archdiocese of Đakovo-Osijek in Đakovo, Croatia. [SEP] Knowledge 2: St. Peter's Basilica
The Papal Basilica of St. Peter in the Vatican (Italian: Basilica Papale di San Pietro in Vaticano), or simply St. Peter's Basilica (Latin: Basilica Sancti Petri), is an Italian Renaissance church in Vatican City, the papal enclave within the city of Rome. [SEP] Knowledge 3: Vatican City
The name Vatican city was first used in the Lateran Treaty, signed on 11 February 1929, which established the modern city - state. The name is taken from Vatican Hill, the geographic location of the state. ``Vatican ''is derived from the name of an Etruscan settlement, Vatica or Vaticum meaning garden, located in the general area the Romans called vaticanus ager,`` Vatican territory''.
Knowledge 1: Đakovo Cathedral
The Đakovo Cathedral or Cathedral basilica of St. Peter () is the cathedral of the Roman Catholic Archdiocese of Đakovo-Osijek in Đakovo, Croatia. [SEP] Knowledge 2: St. Peter's Basilica
The Papal Basilica of St. Peter in the Vatican (Italian: Basilica Papale di San Pietro in Vaticano), or simply St. Peter's Basilica (Latin: Basilica Sancti Petri), is an Italian Renaissance church in Vatican City, the papal enclave within the city of Rome. [SEP] Knowledge 3: Mosaic
Later fresco replaced the more labor-intensive technique of mosaic in Western-Europe, although mosaics were sometimes used as decoration on medieval cathedrals. The Royal Basilica of the Hungarian kings in Székesfehérvár (Alba Regia) had a mosaic decoration in the apse. It was probably a work of Venetian or Ravennese craftsmen, executed in the first decades of the 11th century. The mosaic was almost totally destroyed together with the basilica in the 17th century. The Golden Gate of the St. Vitus Cathedral in Prague got its name from the golden 14th-century mosaic of the Last Judgement above the portal. It was executed by Venetian craftsmen.
Knowledge 1: Đakovo Cathedral
The Đakovo Cathedral or Cathedral basilica of St. Peter () is the cathedral of the Roman Catholic Archdiocese of Đakovo-Osijek in Đakovo, Croatia. [SEP] Knowledge 2: Westminster Abbey
The abbey was restored to the Benedictines under the Catholic Mary I of England, but they were again ejected under Elizabeth I in 1559. In 1560, Elizabeth re-established Westminster as a "Royal Peculiar" – a church of the Church of England responsible directly to the Sovereign, rather than to a diocesan bishop – and made it the Collegiate Church of St Peter (that is, a non-cathedral church with an attached chapter of canons, headed by a dean.) The last of Mary's abbots was made the first dean. [SEP] Knowledge 3: Valencia
On 9 July 2006, during Mass at Valencia's Cathedral, Our Lady of the Forsaken Basilica, Pope Benedict XVI used, at the World Day of Families, the Santo Caliz, a 1st-century Middle-Eastern artifact that some Catholics believe is the Holy Grail. It was supposedly brought to that church by Emperor Valerian in the 3rd century, after having been brought by St. Peter to Rome from Jerusalem. The Santo Caliz (Holy Chalice) is a simple, small stone cup. Its base was added in Medieval Times and consists of fine gold, alabaster and gem stones.

Answer: 11 February 1929