For eggs with a strange odor, it’s best never to eat them. This also applies to eggs stored in the fridge or in a basket on the table... In general, eggs (fresh or boiled) should never be exposed to sunlight. The sun can spoil any egg in just a few hours.

Nevertheless, it is a good rule of thumb not to eat boiled eggs older than 5 days under any circumstances. Some nutritionists claim that hard-boiled eggs can be up to 7 or even 8 days old, but it is much better to throw them away after just a few days.

Old eggs can be most easily recognized by the yolk, which turns green. The more green there is, the less fresh the egg is.

More!

Although the yolk becomes green because of a reaction between the yolk and the white, this means chemical reactions have started to occur, which are not always safe. This can heavily damage your overall metabolism, as well as internal organs.

This means that smell is still the best indicator of whether an egg is fresh.