Answer: The Eon takes the longest amount time to change.
Explanation:
The Eons subsystem is the largest of geological time. They are roughly about hundreds of millions of years in length on the time scale. In the time scale the Phanerozoic Eon is the latest eon and began more than about 500 million years ago.
Eons are sub divided into smaller time units called eras.
Eras are further subdivided into smaller units called periods. The events that occur during the periods are wide-spread in extent but are not as significant as those which occur in the eras.
