four years ago 和 four years earlier 都是表示四年以前吗?

four years ago 和 four years earlier 都是表示四年以前吗? four years Mrs White left America four years ago four years ago翻译成中文是什么意思? 译：four score and seven years ago... every four years 和each four years哪一个对 Selina lived in America four years ago(对画线的部分提问：four years a Four Years Old 歌词 four years before four years,over Four years' school life some four years later