Bananas tend to stay fresh for two to seven days on the counter and two to nine days in the refrigerator. However, it can be difficult to determine the precise amount of time it takes a banana to rot because there is not a "sell by" date.
Rotten bananas are brown and leak fluid. Eventually, rotting bananas turn completely black and grow mold. While bananas tend to rot quickly, there are a few ways to extend their shelf life. For example, store bananas away from other fruits. Another way to extend the life of a banana is to place it in the refrigerator to slow down the ripening process.