The Bundestag works in Sitzungswochen, sitting weeks, at least 20 a year. The Council of Elders sets their dates early, for the following year. The agendas, by contrast, are agreed shortly before each week. Every sitting week has the same shape. On Tuesday afternoon the parliamentary groups meet. On Wednesday the committees meet. Plenary sessions run all day on Thursday and until the afternoon on Friday. The second chamber, the Bundesrat, keeps its own rhythm. It meets in public session every three weeks, on a Friday, except during the summer break.