How long can a chicken egg remain outside before it goes bad?

Eggs left outside for more than 36 hours should be suspect especially if you have a rooster. Eggs found hidden outside can be tested for freshness in two ways. Candling is a good way to know if changes have taken place inside the egg. If the temperature has been hot and a high humidity above 60% , there very well could be the start of a chick embryo inside the egg. The other way to tell is the "float test". As the egg ages, moisture is lost through the porous egg shell and is replaced by air. A stale or bad egg will float if placed into a bowl of water.