Expiration dates are often misleading. Eat By Date is a giant database of food products that gives you true expiration dates, plus a lot of other useful information.
You can search or browse for a food item, and the site will tell you how long that item lasts when unopened or when stored in the fridge or freezer.
The site uses information from the US Department of Agriculture and the Food and Drug administration. It's similar in many ways to the previously mentioned StillTasty.
But at Eat By Date, many food items come with a lengthy explanation and additional info. It tells you how to tell if certain foods are bad, and what happens when those foods go bad. It offers various tips for storage and other interesting facts too. For example, here's what it says on how to tell if peanut butter has gone bad:
A common trait of bad peanut butter is a change in texture from soft and creamy to hard and dry. The colour of the spread may also become darker and the pleasant aroma disappears...
A natural separation of oil is natural, especially in the natural peanut butters that do not contain additional fats as stabilizers. You can tell how long the jar of peanut butter has been sitting on the shelf by the amount of oil on top. This oil can be stirred back into the peanut butter if desired, but we prefer to pour most of it into a frying pan and use it for pan frying something for dinner. The resulting peanut butter is thicker and doesn't gush right out of your sandwich. On the other hand, if oil begins to separate from processed peanut butter (Peter Pan, Jiffy, etc.) that is an indication that the peanut butter will soon be going bad.
It's a lot of useful information, and it also offer handy charts for quick info. Check it out at the link below.