Any food which 'from a microbiological point of view, is highly perishable and in consequence likely after a short period of time to constitute an immediate danger to human health' is required to have a 'Use By' date. Most chilled foods come into this category.
The following example is from the front panel of a box containing 'Cheese and Tomato Quiche':
The 'Use By' date is the legal requirement - the 'Display Until' date is for the store to ensure that the product is sold with enough time for the consumer to still enjoy the food. Notice also that the storage conditions necessary for the safety of the product are given next to the 'Use By' date, 'Keep refrigerated below 5°C'.