It is called Leap Year, and the day that is added is February 29th. We only get that day once every four years.
A triennial event happens every three years.
Something that happens every six years is sexennial.
Something that happens every three years is a triennialevent.
The practice of adding a day to the calendar, known as a leap day, began with the Julian calendar introduced by Julius Caesar in 45 BCE. The purpose of adding an extra day in February every four years was to account for the difference between the solar year and the calendar year.
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.
Your mom happens every two years. U.S. Senators are elected to serve terms of 6 years and terms are staggered so that about 1/3 of the Senate seats are up for election every two years.
the world cup ( I think) happens every 3 years or 4 years?
the Olympics
It happens every 200 years.
The Olympics.