The president of the Bundestag is elected during the constituent session of each election period after the federal elections or in a later session, if the office has fallen vacant, by all members of the Bundestag. The president has to be a member of the Bundestag. Until the election of the president, the session is chaired by the father of the House, the so-called "Alterspräsident". Since 2017, this has been the longest serving member of the Bundestag; in 1949-2017, it was the oldest member of the Bundestag by age.