We all have them. Those foods that have been sitting in our fridges or pantries for, well, that's the problem, we don't really know how long. The expiration date can be confusing because oftentimes it refers to how long said product lasts before we start using it. But, we want to know if our jam is still good even though we opened it close to a year ago, or if that miso paste we only used once needs to bite the dust.For answers, we turned to the professionals — USDA's Marianne H. Gravely, a technical information specialist, and the USDA Foodkeeper app . If you've never tried the Foodkeeper app, we highly recommend it. You can check how long just about anything stays good after being opened. Plus, there's a calendar tool that will remind you when to chuck that loaf of bread you froze, or the bag of flour you used to make a cake last Christmas.Ahead, find 11 common eats (most of which are probably sitting open in your fridge or pantry right now) that tend to cause confusion when it comes to how long they actually stay good. (It's probably high time to throw a lot of them away.) Because, as it turns out, peanut butter doesn't really last forever.