An eon is a very long period of time, used primarily in geology and astronomy to describe vast stretches of Earth's history or the age of the universe.

In Geology:

• An eon is the largest division of geological time.
• It typically spans about 1 billion years or more.
• For example, the Phanerozoic Eon , which includes the time from the appearance of most major animal groups to the present, started around 541 million years ago and continues today.

In Astronomy and Cosmology:

• The term "eon" can be used more loosely to describe extremely long periods, often billions of years.

Summary:

• 1 eon ≈ 1 billion years (1,000,000,000 years)

If you want more detail about specific eons or how they fit into Earth's history, feel free to ask!