backdate
verb [ T ] uk/ˌbækˈdeɪt/ us/ˈbæk.deɪt/
使（尤指涨工资）在较早的时间生效
to make something, especially a pay increase, effective from an earlier time
They got a pay rise in March that was backdated to January. 他们3月份涨了工资，而实际加薪是从1月份算起的。
Compare: predate (BE BEFORE)postdate (HAPPEN AFTER)