Egg cartons from plants producing U.S Department of Agriculture (USDA)-graded eggs must display a Julian date – the date the eggs were packed. Although not required, egg cartons may also carry an expiration (sell-by) date and/or a best-by (use-by) date. Expiration dates are included on some egg cartons ensuring retailers do not keep eggs on shelves past a certain date. However, eggs can be safely eaten 2-3 weeks beyond the expiration date. Depending on the state, the expiration date may be labeled as SELL BY, USE BY, EXP BY or BEST BY. On USDA grade-shielded egg cartons, if an expiration date appears, it can be no more than 30 days after the pack date. It may be less than 30 days through the choice of the packer or quantity purchaser, such as your local supermarket chain. On USDA grade-shielded egg cartons, if a best-by (use-by) date appears, it can be no more than 45 days after the pack date. Eggs that are not packed under USDA's grading program must be labeled and coded in accordance with egg laws in the state where they are packed and/or sold. Most states require the use of a Julian date.
– See Julian Dates, Expiration Date