In the area of the Lviv church province the coexistence of Christians of the Greek and Latin traditions had developed for centuries. After the introduction of the church union in the dioceses of Lviv and Przemyśl at the beginning of the 18th century, the entire Christian population found itself within the Catholic Church. Despite the doctrinal community, Catholics of various rites were subject to different religious customs and functioned according to different calendars. During the widespread nationalisation of the local people on the basis of religious traditions, various national identities emerged, becoming more and more radical and hostile to each other. Hence, on the ecclesiastical level, initiatives appeared to alleviate tensions and introduce order and harmony resulting from Christian teaching. Concordia of 1863 was such an attempt at an agreement, which under the canon law consolidated the established customs that had been present in the religious life of Galicia for centuries.