time it takes the earth to revolve around the sun
A 2000-year time period is known as a millennium.
A century
lustrum
The period of time that the school year is divided into is called a "term." Each term typically consists of several weeks or months during which students attend classes and complete coursework.
fiscal year
It COULD be called a Gigayear, but in practice it is simply called "a billion years".
Well, darling, a period of one year is called a "year." It's not rocket science, sweetie. Just like how a period of one month is called a "month." Keep it simple, honey.
It is called the planet's period.
It is called a year because it takes that much time to complete one orbit of the sun.
A time a person rules is called a 'Ruling Period' or 'Reign'
The time a planet takes to revolve around the sun is called its orbital period.
A ten year period is a decade.