When properly stored in a refrigerator, fresh eggs are good 3 to 4 weeks past their “use by” date. If you want to know if an egg has gone bad without cracking its shell, you can try the egg float test. Although it is not 100% accurate, it will give you an idea if the egg is worth breaking or not.
To conduct the egg float test, all you need to do is submerge the egg in water. A good egg will sink to the bottom and remain on its side. An egg that stands with the larger or wider end towards the top is older, but still edible. An egg that floats or hovers near the surface of the water indicates that bacteria has broken down the proteins found in egg whites and have created gases which make the egg unsafe to consume.
Since the egg float test is not an exact science, you may end up throwing out a perfectly good egg – however, when it comes to your health, it is better to err on the side of caution. Your health is not worth the cost of 1 (or a dozen) eggs.