What does AD mean?

Context:

BEIJING - The following is the biographical sketch of Xi Jinping:
Xi Jinping, born in June 1953, is a male ethnic Han from Fuping, Shaanxi Province. He entered the workforce in January 1969 and joined the Communist Party of China (CPC) in January 1974. He graduated from the School of Humanities and Social Sciences at Tsinghua University with a major in Marxist theory and ideological and political education, has an in-service postgraduate education and holds the degree of Doctor of Laws.
He is currently general secretary of the CPC Central Committee, chairman of the CPC Central Military Commission, vice president of the People's Republic of China (PRC), vice chairman of the PRC Central Military Commission, and president of the Central Party School.
1969-1975 Educated youth and Party Branch secretary, Liangjiahe Brigade, Wen'anyi Commune, Yanchuan County, Shaanxi Province
1975-1979 Student of basic organic synthesis, Department of Chemical Engineering, Tsinghua University
1979-1982 Secretary, General Office, State Council and Central Military Commission (AD)
1982-1983 Deputy secretary, CPC Zhengding County Committee, Hebei Province
1983-1985 Secretary, CPC Zhengding County Committee, Hebei Province; concurrently first commissar and Party Committee first secretary, Zhengding County Military Affairs Department
1985-1988 Member, Standing Committee, CPC Xiamen Municipal Committee, Fujian Province; and vice mayor, Xiamen