Out of Stock items can specifically be checked by selecting the Out of Stock filter in the top left corner as shown below.

Once you have this list selected, pick the item you are looking for from the list on the right and find it on the store shelf.  If there is now stock of that item on the shelf, you should check every instance of that item on the shelf to make sure that you can enter the next closest date to today.  Click on the item.  

Once you have clicked on the item it will bring you to the screen to enter the next expiration date. Enter the "Next Closest Date" and hit submit.

If you have selected an item and the item is still out of stock or has been discontinued from the store, you can also select those buttons on the left and right side of the number pad, respectively.