Test an egg for freshness by submerging it in a bowl of water. Eggs that are very fresh have a small air cell, so they sink to the bottom and lie on their sides. Older eggs are vuoyed by an air pocket that gets bigger as water evaporates through the pores in the shell. These eggs tilt large end up in the water. Eggs keep four to five weeks beyond their packing date without significant loss in quality. After that time, if they've been constantly refrigerated, they are more likely to become dry due to moisture loss than they are to spoil.
