Historical list of leap seconds since 1972

Date Introduced	+ve/-ve leap second	TAI - UTC (seconds)
1 Jan 1972	+ve	10.0
1 Jul 1972	+ve	11.0
1 Jan 1973	+ve	12.0
1 Jan 1974	+ve	13.0
1 Jan 1975	+ve	14.0
1 Jan 1976	+ve	15.0
1 Jan 1977	+ve	16.0
1 Jan 1978	+ve	17.0
1 Jan 1979	+ve	18.0
1 Jan 1980	+ve	19.0
1 Jul 1981	+ve	20.0
1 Jul 1982	+ve	21.0
1 Jul 1983	+ve	22.0
1 Jul 1985	+ve	23.0
1 Jan 1988	+ve	24.0
1 Jan 1990	+ve	25.0
1 Jan 1991	+ve	26.0
1 Jul 1992	+ve	27.0
1 Jul 1993	+ve	28.0
1 Jul 1994	+ve	29.0
1 Jan 1996	+ve	30.0
1 Jul 1997	+ve	31.0
1 Jan 1999	+ve	32.0
1 Jan 2006	+ve	33.0
1 Jan 2009	+ve	34.0
1 Jul 2012	+ve	35.0
1 Jul 2015	+ve	36.0
1 Jan 2017	+ve	37.0