10

This is an American military term that means, "Come to attention!" It was shortened from X and came into use because it is easier to say at full shout than Y

And the answer is

Ten hut

shORTENED from AT-TEN-TION

Essentially throughout history many have been claimed to be this and the respective reasons are as follows:

1543:

1) Andreas Vesalius publishes "De humani corporis fabrica" (On the Fabric of the Human Body), revolutionising the science of human anatomy and 2) Nicolaus Copernicus publishes "De revolutionibus orbium coelestium" (On the Revolutions of the Heavenly Spheres) in Nuremberg.

this is as the title of a poem composed by English poet John Dryden about the events of 1666

1666-

1) Great fire of london

2) the English fleet defeated a Dutch fleet in the St James' Day Battle, for a great victory at sea.

3) Isaac Newton made revolutionary inventions and discoveries in calculus, motion, optics and gravitation.

1759- A series of victories by the British military in 1759 in North America, India, and in various naval engagements, is occasionally referred to as this and was the decisive year of the Seven Years' War

1905- Albert Einstein made important discoveries concerning the photoelectric effect, Brownian motion and the special theory of relativity

1922 -publication of many major literary works, including James Joyce's Ulysses and TS Eliot's The Wasteland.

And the answer is

ANNUS MIRABLIS

WONDERFUL YEAR OR YEAR OF WONDERS