Passage: Di Rupo came in contact with the socialist movement for the first time during his studies in Mons, where he first obtained a master's degree and afterwards a PhD in chemistry. He went during the preparation of his doctorate to the University of Leeds (United Kingdom), where his function was that of lecture member of staff in 1977–1978.He started his political career as an attaché at the cabinet of Jean-Maurice Dehousse in 1980–81. His first political mandate came in 1982, when he was Councillor of Mons (until 1985, and again from 1988 until 2000). In 1986, he was mayor of health, urban renewal and social affairs. Professionally, Di Rupo was at the same time cabinet member and then Deputy Head of Cabinet of the minister of finance of that time of the Walloon region and consequently Deputy Head of Cabinet of the minister of finance and energy of the Walloon region at that time Philippe Busquin (1981–85) and superintendent of the energy-inspection of the ministry of the Walloon region.He is a deputy (MP) for the Arrondissement of Mons in the Belgian Chamber of Representatives. He once described François Mitterrand as being "a character from a novel".In 2000, he became the mayor of Mons, which is the capital of the province of Hainaut.

Question: When was he mayor?
1986