It is a 'millennium' that is a period of 1,000 years.
a five-year period is a quinquennium
A period of ten years is a decade.
It's called a decade.
Can also be called a Decade.
A period of ten years is called a decade. Sometimes a decade is used more specifically, to refer to a ten-year period that starts with a year that ends in zero. For example, "the sixties" or "the 1960s" refers to the years 1960-1969.
A ten year period is a decade.
A period lasting ten years, or any ten year period.
The minimum period is two years and can be as long as ten years.