O nascimento de Christ  é um grande marco. Porém in English ele é represented de um modo um pouco different:

BC = Before Christ

      * BC represents the years BEFORE Christ was born;
      * BC deve estar sempre AFTER the number.

      Eg.: Cleopatra died in 30 BC in Alexandria. She was 39 years old.

AD = Anno Domini

      * Anno Domini means “the year of our Lord” in Latin;
      * AD represents the years AFTER Christ was born;
      * AD deve estar sempre BEFORE  the number.

      Eg.: This Roman painting is from the year  AD 1.

Wanna know more?  Access the original https://simple.wikipedia.org/wiki/Anno_Domini to expand your   culture.