I think the way to refer to this would be retrospective, and I'll clarify the distinction there. It would be looking at the period of time for which an employee has been working with an employer, and so that could be looking at a period of time that predates a coming into force, assuming that this comes into force.
So it would be looking backwards to determine when the employee started to work for the employer. However, as to when an employee would be eligible to receive or be eligible to take those days of paid sick leave, that would be moving forward—so from the time that this legislation would come into force, assuming that it gets passage.
That would be the distinction between retroactive and retrospective. It would look backwards to consider the period of employment with the employer.