Capitalization: Periods and Events

Specific periods, eras, historical events, etc.: these should all be capitalized as proper nouns. Why? Since there are many periods, eras, wars, etc., the capital will differentiate the specific from the common. Consider the examples below:

Most of the World War I veterans are now deceased.

In the Middle Ages, poor hygiene was partly responsible for the spreading of bubonic plague.

The McCarthy Era inspired Arthur Miller to write The Crucible.

Roman Britain is the setting for the Minimus comic books.

Middle school students often enjoy studying the social changes that took place in the Roaring Twenties.

However, centuries—and the numbers before them—are not capitalized. See the examples below for an illustration of this rule:

In the fifteenth and sixteenth centuries, England blossomed into an empire.

In the eighteen hundreds, the world saw great technological advancement.