To ensure your no-bake cheesecake is properly frozen and ready for tomorrow, it's best to leave it in the freezer for at least 4 to 6 hours. However, for the best results and to allow ample time for the cheesecake to freeze thoroughly, I recommend leaving it in the freezer overnight.
Based on the information you provided, if you put the cheesecake in the freezer at 7:40 p.m., it should be frozen and ready to be served the next day by the morning or early afternoon.
Keep in mind that the exact freezing time may vary slightly depending on the size and thickness of the cheesecake and the temperature of your freezer. Freezing it overnight will give you the assurance that it has plenty of time to set and achieve the desired consistency for serving.