This is one topic/thread I have not come across after 3 years on this site. I was at friends house getting four 2 week old BSLs(stupid chicken math). This subject came up and never knew how to read the box. Figured I would pass it along to the long timers as well as the newbies and everybody in between that is not privy to this info. I figure it is a good selling point to customers( at least the skeptical ones on fresh eggs).
Beyond the sell by date is the more important pack date or "Julian" date. What it refers to is the actual day of the year. Such as January 1 would be 001 and December 31 would be 365 unless it is a leap year then it would be 366. So this example the date would be on or about July 27(221st day of the year). USDA says you can't date beyond 6 weeks from the pack date. I figure it is a good teaching and selling tool to your egg customers. Pending where you live commercial eggs could be be days to weeks old before they hit the shelves more so in the bigger box stores.