In Zile Singh v. State of Haryana (2004), the Supreme Court restated a cardinal principle of…

Every statute operates from the date the Bill was introduced, unless it states otherwise

A statute is prima facie prospective unless made retrospective expressly or by necessary implication

Every statute is retrospective if it is remedial, whatever its effect on vested rights

Every statute is prima facie retrospective unless it is expressly or impliedly made prospective