The oldest Sabor with extant records was held in Zagreb on 19 April 1273. This was the Sabor of Slavonia, and not of Croatia and Dalmatia. The earliest Sabor of the Kingdom of Croatia and Dalmatia dates to 1351. The Parliament session held in 1527 in Cetin affirmed the House of Habsburg as Croatian rulers. After this, the Sabor became a regular gathering of the nobility, and its official title gradually stabilised by 1558 as the Parliament of the Kingdom of Croatia and Slavonia. Since 1681, it has been formally called the Diet of the Kingdom of Croatia, Dalmatia and Slavonia. In 1712, the Sabor once again invoked its prerogative to select the ruler, supporting what later became the Pragmatic Sanction of 1713. Since the mid-1800s, the Sabor has regularly met and its members have been regularly elected. Exercising its sovereignty once again on 29 October 1918, the Sabor decided on independence from Austria-Hungary and formation of the State of Slovenes, Croats and Serbs which later joined the Kingdom of Serbs, Croats and Slovenes. The Sabor did not meet between 1918 and 1945, except for an unelected Sabor convened in 1942. The Sabor initially reconvened as an assembly of State Anti-fascist Council for the National Liberation of Croatia (ZAVNOH) in 1943 and evolved since through various structures following the November 1945 elections and several changes of the constitution. After the first multi-party elections since Communist rule and the adoption of the 1990 constitution, the Sabor was bicameral (Chamber of Representatives and Chamber of Counties) until 2001, when constitutional amendments changed it to the unicameral form currently used.