The "best before" date printed on a case of beer indicates that the beer might not taste as good after that time. However, states don't all require that expiration dates get printed on the case box. When it doesn't appear on the case, the date can be found in codes located elsewhere in the beer packaging, such as on the bottom of a can, or on the neck or shoulder of a bottle.
Check the case box for an expiration date. Look at the bottom, sides and top of the box for either a "Best Before" date, "Packaged On" date or "Sell By" date. The date could also be on one of the cardboard flaps when you open the box. The date could be written in several formats signifying year, month and day such as yyyy,mm,dd; mm,yy; dd,mm,yy. The beer remains drinkable for six months past the packaging date.
Look on the bottom of a beer can. The expiration date could be plainly printed on the bottom, or a code might reveal the shipping date or bottling date of the beer. Check the first six to seven digits of a code appearing on the bottom of the can; if you are drinking the beer within 180 days or about six months of the date printed on your can, it has not expired.
Search for a code printed on the neck or shoulder of a beer bottle. The first letters represent the month of brewing; the following digits indicate what day of the month and the year. The two letters on the end of the code are an abbreviation for the state in which the beer was brewed. Determine whether you're within six months of the packaging date.
You can drink expired beer without harm; it might have an off or unpleasant taste, however.