So, if these are points awarded on June 1, 2018 and you bank them, they enter your 2019 UY, and must be used by May 31, 2020. So no, cannot use for August 2020.
You could try either putting them up for transfer. Technically not allowed to be done for profit so it's a touch risky, but doable. Or you could add a night to your current trip, and make up any difference in points needed with OTU points. Or trade them into RCI, they are good for longer once traded in. Or just let them go to waste, but that's just sad.