Fitted or designed to retroact; operating by returned action; affecting what is past; retrospective
If a decision or action is retroactive, it is intended to take effect from a date in the past. There are few precedents for this sort of retroactive legislation. = retrospective + retroactively retro·ac·tive·ly It isn't yet clear whether the new law can actually be applied retroactively. = retrospectively. a law or decision that is retroactive is effective from a particular date in the past = retrospective
extending in scope, effect, application or influence to a prior time or to prior conditions