That's called a millenium.
There are 25 years in a quarter of a century.
It COULD be called a Gigayear, but in practice it is simply called "a billion years".
25 years = 788,923,149 seconds.
1/25 Hz
A period of 25 years is commonly referred to as a "quarter-century."
A period of seven years is called a septennium.
generation
sevennenium
A quarter century.
A quarter century.
100 years is a "century."
term millennium
A decade.
One quarter. A century is 100 years, therefore 25 years is one quarter of that period (because 4 x 25 = 100).
Its called a century! century means 100 years and decade means 10 years
Celebrating 25 years of marriage is called the Silver Anniversary.