In a YouTube video posted by the folks at America's Test Kitchen, editor-in-chief of Cook's Illustrated magazine, Dan Souza, explains the shockingly simple yet seemingly little-known way to figure out when your eggs were packed. As he details, you just need to find the three digit number right near the "best by" date. That number is known as the Julian date, and signifies the number of the day in the calendar year on which the carton was packed. So, for example, 001 would mean the eggs were packed on January 1, 004 signifies they were packed on January 4, so on and so forth through 365, which means they were packed on December 31. Souza recommends using this handy trick to locate eggs that are less than three weeks old in order to make the tastiest egg-involved recipes.