Quadrenial
decennial Occurring every ten (10) years. Also tenth anniversary
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.
Something that happens every 25 years is referred to as a "quindecennial." This term is derived from the Latin roots "quinque" meaning five and "decem" meaning ten, collectively signifying a period of 25 years. Quindecennial events can include anniversaries, celebrations, or other recurring occurrences.
pentennial
tercentennial
Every 100 years is called a century, made up of 10 decades.