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.
I believe that the constitution states that one is to be done every 10 years.
The President of The United States of America is inaugurated.
The U.S. Census is used to tell which states grew to get representation and which states lost population and therefor lose some representatives
A census is done on the population. This is important because the representatives in the house is based on the population of each state.
An event that occurs every 100 years is known as a centennial. This term is commonly used to refer to significant anniversaries or celebrations that take place once every century. It is derived from the Latin word "centum," meaning one hundred.
Quadrenial
A triennial event happens every three years.
Something that happens every three years is a triennialevent.
Something that happens once a century.
Something that happens every six years is sexennial.
Something that happens every 5 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.
tercentennial
pentennial
Every 100 years is called a century, made up of 10 decades.
Biennial or biannual can refer to something which happens every two years.