n.
1.the earliest eon in the history of the Earth from the first accretion of planetary material (around 4,600 million years ago) until the date of the oldest known rocks (about 3,800 million years ago)
Idiom of the Day
make hay while the sun shines
to do something at the right time, to take advantage of an opportunity
We will make hay while the sun shines and paint the house while the weather is good.