You can check to see how old an egg is easier than that. If you put an egg in just plain clean water, like a kitchen sink of water, a fresh egg will sink to the bottom and lay on it's side, an old egg will float and the ones laid in between, will be, well, in between! That's what I do to check eggs I find hidden like that, as soon as I find them. If any even stand on their end, upright in the water, I just feed them back to the chickens.
The floaters, I bury in the compost pile, so they don't get broken and stink! Stinkers, as I call them, really do smell quite awful !!!