How long does it take to regain vision after a stroke?

Hard to say. It depends on the degree of the stroke, the exact location of the stroke and how quickly the stroke was treated. It could be hours to days to weeks or possibly never.
Lots of variability. Vision recovery after a stroke depends on the particular brain regions affected. In general, much of the functional recovery that occurs after a stroke occurs within the first month, but recovery can continue to occur for a year or more after a stroke.