If you need the no-bake cheesecake for tomorrow, it's best to freeze it for at least 4-6 hours to ensure it sets properly. However, if you can leave it in the freezer overnight, that would be even better, as it will have ample time to firm up and reach the desired texture.
Given that you put the cheesecake in the freezer at 7:40 p.m., freezing it overnight means leaving it in the freezer until the next morning. Depending on your plans for the cheesecake, you can take it out of the freezer an hour or two before serving to allow it to thaw slightly and soften just enough to be easily sliced and enjoyed.
If you're concerned about the exact timing, you can check on the cheesecake's consistency after 4-6 hours in the freezer. It should be firm to the touch and hold its shape when you gently press down on it. If it meets this criteria, you can consider it ready to be taken out of the freezer for tomorrow's consumption.