By putting them into a water-filled container or glass, it is possible to determine if the eggs are fresh or otherwise:
Very fresh: A very fresh egg will sink to the bottom and lay on its side.
Week old: One week old eggs will rest on the bottom but the fat end will rise up slightly.
3 week old: Three week old eggs will be balanced on pointy end with the fat end sticking up.
Bad Eggs: Old eggs will be floating bobbing along the surface of the water. These floaters should be tossed as they aren't any good to eat.
Hope that helps.
