Tenure of office: 01 Jul 1979 — 31 Aug 1988, Feb 1992 — Jul 1992
Tenure of office: 01 Aug 1988 — 31 Aug 1991
Tenure of office: 01 Sep 1991 — 31 Jan 1992
Tenure of office: 01 Aug 1992 — 31 Jul 1998
Tenure of office: 01 Aug 1998 — 31 Jan 2002, 01 Aug 2014 — 31 Jul 2015
Tenure of office: 01 Feb 2002 — 31 Jan 2008
Tenure of office: 01 Feb 2008 — 31 Jul 2011
Tenure of office: 01 Aug 2011 — 31 Jul 2014
Tenure of office: 01 Aug 2015 — 31 Jul 2018
Tenure of office: 01 Aug 2018 — 31 Jul 2021
Tenure of office: 01 Aug 2021 — 31 Jul 2022
Tenure of office: incumbent, 01 Aug 2022 —present