We often have mystery containers in our fridge -- some Tupperware with leftover turkey meatballs or salmon from the grill, a Ziploc bag containing some extra steamed broccoli, maybe even some takeout from a favorite restaurant. We always have good intentions when it comes to consuming this stuff, but the days usually get away from us and we end wondering how long our foods have been chilling on their respective shelves. So we toss them, just to be safe. If only we could remember when we started storing our leftovers, we'd know when exactly to toss them.

We've got about three to four days to eat our cooked leftovers, says the USDA. This goes for cooked meat and poultry, mayonnaise-based goods (egg, tuna, or macaroni salads, for example), and takeout. Want to make your foods last longer? Freeze them, and they'll stay good for two to six months. Not the mayo foods, though. Don't freeze these.

Another recommendation: Ditch any meat, poultry, eggs, or casseroles that have been sitting at room temperature for more than two hours. If the temp is more than 90 degrees, trash after one hour. Keep this in mind when setting out your Thanksgiving spreads. One last suggestion: Experts agree that you can't judge food safety by smell or taste -- so when in doubt, throw it out.