How do historians identify one era as separate from another era

They identify eras based on the events that occurred in that era.

Explanation:

For example, classic music was popular during the 1750-1820 so it's called the Classic Era. The 1950s-1990s was known as the Civil Rights Era. And what we all are experiencing now which is 2020-indefinite time, which is known as the Corona-virus Era.

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polticians and sentates thought to annoucne the fialre of articles of confedartion by making a centralized nation as a hole