Konrad Bitz, the Bishop of Turku, marks the date of his preface to Missale Aboense, the oldest known book of Finland.

The Archdiocese of Turku is the oldest diocese in Finland. Medieval bishops of the Catholic Church were also de facto secular leaders of the country until the end of the 13th century.

The Archdiocese of Turku, historically known as Archdiocese of Åbo, is the seat of the Archbishop of Turku. It is a part of the Evangelical Lutheran Church of Finland, and its see city is Turku.

Missale Aboense was the first book printed for Finland. As its name suggests, it was a prayer book used for Mass. It follows the tradition of the Dominican liturgy, which around the year 1330 was adopted as the official liturgy of the See of Turku. This poor bishopric could not afford to have its own missal printed, but its Dominican tradition came to the rescue.

Finland, officially the Republic of Finland, is a Nordic country in Northern Europe. It borders Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of Bothnia to the west and the Gulf of Finland to the south, opposite Estonia. Finland has a population of 5.6 million, the majority being ethnic Finns. Its capital and largest city is Helsinki. The official languages are Finnish and Swedish, the mother tongues of 84.1 percent and 5.1 percent of the population, respectively. Finland's climate varies from humid continental in the south to boreal in the north. Its land is predominantly covered by boreal forest, with over 180,000 recorded lakes.

August 17 is the 229th day of the year in the Gregorian calendar; 136 days remain until the end of the year.