What is a retrospective or retroactive statute?

Elmer A. Driedger in his book, The Construction of Statutes (1974), after considering the above quote from Phillips v. Eyre, said as follows at p. 140 of that volume: What is a retrospective or a retroactive statute? These words are derived from Latin root words meaning "looking" or "operating", and "backwards". A retrospective statute must therefore be one that is operative with respect to a time prior to its enactment. A statute or a provision thereof may be made retrospective in one of two ways: either it is stated that it shall be deemed to have come into force at a time prior to its enactment; or it is expressed to be operative with respect to past transactions as of a past time, as, for example, the Act of Indemnity considered in Phillips v. Eyre. Unless, therefore, a statute alters a right as of a prior time it cannot correctly be called retrospective within the normal meaning of that word.