That's called a millenium.
It COULD be called a Gigayear, but in practice it is simply called "a billion years".
It is a millennium that is equivalent to a thousand years.
It depends on where you live. In the US there are a thousand millions in a billion. In Great Britain, what Americans call a billion is called a thousand million, and there are ten thousand millions in a British billion, or what Americans call a trillion.
Without careful, precise, lab-grade measurement, anyone who looked at it would call it a "circle".
Seven million, fifty thousand.
term millennium
Its called a century! century means 100 years and decade means 10 years
It COULD be called a Gigayear, but in practice it is simply called "a billion years".
a millennium
Procession of the Equinox
One thousand years is a millennium, from the Latin "mille" for "thousand". One hundred years is a century, from the Latin "centum" for "hundred".
millennium
generation
sevennenium
It is a millennium that is equivalent to a thousand years.
The period with scarcity of food is called 'famine'
100 years is a "century."