How do I set a product to open and close at a set time (a drop)?

Open Store & Donations, go to Products, and open the product. In the Drop section choose the Time Zone the times are typed in, then set Opens On and Opens At, and, if the sale has an end, Closes On and Closes At. Save the product. Leave both blank to keep selling with no end.

Before the opening time the store shows when the drop opens and takes no orders; after the closing time it shows Ended. Both are checked again at checkout, so a cart that was filled early or late is refused with the opening time or the words This drop has ended. A checkout that started while the drop was open keeps its payment window and can finish even if the close passes during it. Edition Size (for example, Edition of 50) is shown to buyers as information; the Stock count is what stops sales.