What do buyers see before, during, and after a drop?

Every store surface (the product card, the product page, and the Drop block) shows the same state, worked out from the product's opening and closing times, its stock, and its Preorder setting, in this order:

• Before it opens: a clock panel marked Upcoming, with the opening time in the visitor's own time zone and a large countdown in days, hours, minutes and seconds, and no buy button. The Drop block can show an Email me when it opens link here.
• Open: Add To Cart, and when a closing time is set, the same clock panel marked Open now (Closing soon in its last two days) counting down to the close.
• Preorder: the same, with the button reading Preorder and the line Ships by followed by your phrase.
• Sold out: the words Sold out and nothing to press. Under Store Settings, Sold Out can hide sold-out products from the store grid instead.
• Ended: the words Ended (This drop has ended on the product page) and nothing to press.

A visitor watching the page sees the button appear at the opening time and disappear at the closing time without reloading. Checkout applies the same rule on the server.