What is Retrospective Legislation?

Question

What is Retrospective Legislation?

Answer 1

probably the same as  ex post facto

Legislation  passed that changes the law so that a legal act committed in the past is now defined as "has always been illegal"

Answer 2

simply it is a law that aplies backwards for example if a new law that comes out and says blue cars are illigal and every one who alread has a blue car is affected then it is said that the law has applied retrospectively , laws are meant to be applied prospectively fairly and to all