VERB
追溯；使（从过去某个日期）开始生效
If a document or an arrangement is backdated, it is valid from a date before the date when it is completed or signed.
例句
The contract that was signed on Thursday morning was backdated to March 11...
周四早上签订的合同实际生效日期追溯到3月11日。
Anyone who has overpaid tax will be able to backdate their claim to last April.
超额纳税者申领退款可以从去年4月算起。