relation back

noun | re·la·tion back

1. : the assigning of a prior date (as the date of execution of a document) to an act (as filing of a document and especially a pleading) as the time of its effect especially to avoid a time limit the relation back of amendments to the date of the original pleading; also : the legal fiction that an action (as the filing of a document) was taken on a previous date to avoid the expiration of a time limit : the legal fiction that an action (as the filing of a document) was taken on a previous date to avoid the expiration of a time limit