1975

March
April
May
July-August
September
October
November
December

1976

January
February-March
April
May
June
July-August
September
October
November
December

1977

January
April-May
June-July
August-September
December-January (1978)

1978

February-March
June-July
August
December

1979

May
June
July
August
October
November-December

1980

January-February
March
May-June
July

1981

Earth Day

1990

Summer