2021-6-7 · BC (not comparable) . Initialism of Before Christ. The Han Dynasty ruled China from 206 BC to AD 220.; Usage notes []. The Chicago Manual of Style as well as most house styles require placing the AD before the number of the year and BC after, although in casual use either abbreviation can be found in either place.; Some use BCE, for "Before the Common Era", which is more secular in nature, to ...