Egg: Raw, uncooked
Eggs are supposed to be held chilled to prevent spread of bacteria should the egg have any. Here is a quick one pager from the US FDA.
You will know if an egg has spoiled because it will stink very strongly and there will be no mistaking it. I have never encountered an egg that has gone bad in all my decades. They usually just shrink smaller and smaller in the shell and the white gets more watery. Chilling the egg will make it last longer. After 3 weeks it is no longer in peak quality but that doesn't really mean it has gone bad.
Fill a bowl with water and put the egg in. If it floats, its bad. If it sinks and lays flat its fresh. If it sinks but stand up it is fine to eat but getting old. I raise chickens and on occasion I have found a hidden nest of eggs and this trick works great!
I like this trick too. As the egg gets older, it shrinks inside the shell and the air pocket gets bigger, which makes it float higher.
In the US, we wash eggs before sale and refrigerate them to avoid contamination with Salmonella. Europeans handle eggs differently and do not generally find that refrigeration is necessary. Here's a little article about it http://www.latimes.com...
I buy my eggs from a farmer who pastures his hens, so I always keep 6 eggs in a bowl on my countertop unless it's too hot in my kitchen. Your carton of eggs from the grocery store have the expiration date stamped on it.
Those dates on egg cartons are sell-by dates, not use-by dates, and they vary by retailer. http://www.eggsafety.org/blog/202-how-long-do-eggs-keep-in-the-fridge
I just looked at a carton that I grabbed on sale yesterday and it's stamped "use by".
Maybe it's a mistaken stamp. Now I want to go look at all of their egg cartons.
Agree with nutcakes. It will smell terrible. To avoid adding a spoiled egg into batter, thereby ruining the entire batch, I always crack each egg into a bowl first. Crack into a bowl, make sure that it doesn't smell bad, and only then throw it into the batter; do the same with the next, one by one. Also, I've been told that if the egg is spoiled the yolk will be broken, but I am not sure that's true.
This is what I always did. Just use a cereal bowl to break them into beforehand. If they're bad, you'll KNOW.