A triennial event happens every three years.
Something that happens every six years is sexennial.
I believe that the constitution states that one is to be done every 10 years.
Something that happens every three years is a triennialevent.
Something that happens once a century.
As far as I know, nothing special happens every 100,000 years. A full precession cycle takes about 26,000 years.
Quinquennial = something that happens every 5 years. Lustral = also something that happens every 5 years or we could invent: semi-Decennial: where semi is half and Deccennial happens every 10 years.
It happens every 200 years.
The Olympics.
Something that happens every 5 years
the Olympics
the world cup ( I think) happens every 3 years or 4 years?