With the establishment of the Kalmar Union (1397–1523) between Denmark, Norway and Sweden, by about 1416 Copenhagen had emerged as the capital of Denmark when Eric of Pomerania moved his seat to Copenhagen Castle. The University of Copenhagen was inaugurated on 1 June 1479 by King Christian I, following approval from Pope Sixtus IV. This makes it the oldest university in Denmark and one of the oldest in Europe. Originally controlled by the Catholic Church, the university's role in society was forced to change during the Reformation in Denmark in the late 1530s.