How to Determine How Fresh (or Old) Your Eggs Are
The age of eggs doesn’t really matter when you’re frying or scrambling, but we prefer the freshest specimens possible for our Perfect Poached Eggs.
To determine the pack date (which is typically the same day that the eggs were laid), check the end of the carton for a three-digit code known as the Julian date; this is often beneath or above the sell-by date when one is provided. The numbers run consecutively, starting with 001 for January 1, so 078 would indicate that the eggs were packed on March 19. (The Julian date may follow a set of numbers beginning with a “P”; this is a code indicating the packing plant.)
While some sources suggest that you can check freshness by putting eggs in a bowl of water—fresher eggs are more likely to sink, while older ones are more likely to float because the air sack expands over time—we found that wasn’t a reliable test since eggs didn’t float until they were four to six months old. It’s a safer bet to just check the Julian date; try to find eggs that are less than three weeks old.