Learn English – What are the capitalization rules regarding historical periods of time


Why are phrases like "the High Middle Ages" capitalized while e. g. "the sixth century" is not?

Is there a general rule?

Best Answer

In its chapter on numbers (and select other sections), the Chicago Manual of Style has these recommendations:

[9.33 Centuries] Particular centuries are spelled out and lowercased.

  • the twenty-first century
  • the eighth and ninth centuries
  • from the ninth to the eleventh century
  • the eighteen hundreds (the nineteenth century)

[9.35 Eras] Choice of the era designation depends on tradition, academic discipline, or personal preference. Chicago recommends full capitals and no periods.

[8.72 Traditional period names] Some names of periods are capitalized, either by tradition or to avoid ambiguity.

  • the Augustan Age
  • the Common Era
  • the Counter-Reformation
  • the Dark Ages
  • the Enlightenment
  • the Gay Nineties
  • the Gilded Age
  • the Grand Si├Ęcle
  • the High Middle Ages (but the early Middle Ages, the late Middle Ages)

[8.74 Historical events and programs] Names of many major historical events and programs are conventionally capitalized. Others, more recent or known by their generic descriptions, are usually lowercased. If in doubt, do not capitalize.

  • the Boston Tea Party
  • the Cold War (but a cold war, used generically)
  • the Cultural Revolution
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