2016-2021 (current collective agreement)
- March 1, 2012 – February 29, 2016
- March 1, 2008 – February 29, 2012
- March 1, 2004 – February 29, 2008
- September 1, 2000 – February 29, 2004
- September 1, 1997 – August 31, 2000
- September 1, 1996 – August 31, 1997
- September 1, 1994 – August 31, 1996
- September 1, 1992 – August 31, 1994
- September 1, 1988 – August 31, 1991
- July 1, 1985 – August 31, 1988
- July 1, 1983 – June 30, 1985
- January 1, 1981 – June 30, 1983
- January 1, 1979 – December 31, 1980
- January 1, 1977 – December 31, 1978
- January 1, 1975 – December 31, 1976
- January 1, 1973 – December 31, 1974
- January 1, 1971 – December 31, 1972
- July 1, 1968 – December 31, 1970
- August 11, 1966 – June 30, 1968
