I guess I will give my two-cents worth on this subject since I have been selling/delivering the product for nearly 20 years.
To answer the OP question-it is really the "pull date" or date the beer should not be on the shelf to sell. It has not expired, it is quality control mechanism to keep the freshest product to sell to the public.
Date codes have been used internally by breweries for decades to control inventory.
A very small part at the distributor, not the brewery. The code dates are again a quality control issue. I bring back too much beer past the code, be it one day past, I can plan on being talked too or written up. I have seen in my years way too many salesman get unpaid time off for not paying attention to code dates on the product and a few terminated. It is not tolerated for the two distributors I have worked with. Also, the out-of-date product, be it just one day when picked up and returned to the company was promptly opened and poured out. My pay and bonuses have been based on that code date you see. I have carried a code date book everyday for all these years because if I don't have mine on me, I can be sent home without pay for the day. It is that important.
The enemy of beer is light. The whole cold/warm/cold thing is a myth. All beer is bottled cold and most is sold at room temperature. When stored in a cool dark atmosphere beer can last for years.[/QUOTE]
Yes, the enemy of beer is light and it is NOT a myth regarding constant temperature change. The exact reason I would not drink draught beer in the summertime if I lived in a hot/humid climate that the distributors trucks were not a/c. I know of many instances where the beer had either dramatic temperature changes or was too hot for a longer period of time than should have been for rare reasons and that beer was promptly destroyed. As for temperature, I don't really consider 38-45 degrees room temperature. If I went to deliver my product to an account with a broken cooler (that is room temperature), no beer will be delivered. Temperature is very important.
I guess it is more than two-cent I put in. I will also add that A-B InBev products have provided me with a very comfortable living and allowed me to have many nice trip to WDW.