Promotions are a very common aspect of store websites. Most promotions you create will have a set amount of time they are valid for. As a responsible site administrator you may want to know how to stop the promotional page from being displayed in Google’s search results after it expires. To let you do this Google has provided the unavailable_after META tag.
The unavailable_after META tag notifies google that this page is going to expire at this date and time. This allows google to remove it from it’s indexes so that it does not appear in search results after the expiration date.
A helpful feature for any site that uses online promotions.