I hope you've been convinced by now. I really liked this 'one-year's time' example.
I'd like to add that I wouldn't use ten years' jail but ten years' time or something like that. Of course, it doesn't mean that it's incorrect

This winter's day is not the same question. It's really the day of the winter, possession, but there are also lots of examples where we use the apostrophy to indicate some length of time, such as two weeks' holiday or even a fortnight's holiday (no plural

).