Matthew Sweet looks at the founding of the Dada movement 100 years ago in Zurich, as the city celebrates the anniversary with a series of exhibitions and cabarets which run throughout the year. New Generation Thinker Will Abberley visits an exhibition in Oxford that plays with our notion of time as Modern Art Oxford begins a year-long celebration of 50 years, Kaleidoscope, with a show called The Indivisible Present. Janet Street Porter and Michael Grade debate when does a celebrity become a 'national treasure', and what exactly does the term mean?