AP Style A.D. and B.C.

AP Style A.D.

AP Style accepts the abbreviations A.D. and B.C. when referring to specific calendar years.

A.D. is acceptable in all references for anno Domini, which means “in the year of the Lord.”

Given that the full English phrase would read “in the year of the Lord 89,” the abbreviation A.D. is placed before the figure for the year. For example,

  • St. Peter was crucified in A.D. 67.

Do not write, however, “in the fifth century A.D.” Simply writing out “the fifth century” is sufficient. For example,

  • Wrong: The Roman Empire unraveled in the fifth century A.D.
  • Correct: The Roman Empire unraveled in the fifth century.

If A.D. is not specified with a year, then it is presumed to be A.D. Since A.D. is an abbreviation, AP Style requires there to be periods following each letter.

AP Style B.C.

B.C. is acceptable in all references to calendar years in the period before Christ.

Given that the full English phrase would read “in the year 89 before Christ,” the abbreviation B.C. is placed after the figure for the year. For example,

  • John the Baptist was born in year 5 B.C.

With B.C., it is necessary to write “in the fifth century B.C.” If you do not include the abbreviation B.C., it will be presumed to be A.D. For example,

  • Socrates was alive during the fifth century B.C.

Much like A.D., B.C. is an abbreviation and, therefore, AP Style requires there to be periods following each letter.

Important takeaways

  • A.D. is placed before the figure for the year.
  • Do not write, “in the fifth century A.D.”
  • B.C. is placed after the figure for the year.
  • You must write, “in the fifth century B.C.”
  • AP Style requires periods to be placed after each letter in both A.D. and B.C.

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