It sounds like you’re referring to the date code on egg cartons, not just the printed “expiry/best before” date.
In many grocery systems, there are actually a few different markings people miss:
- Pack date (often a Julian date): a 3-digit number like 032 or 145
→ This is the day of the year the eggs were packed (e.g., 032 = Feb 1 in a non-leap year) - Best before / expiry date: usually a marketing-style freshness guide, not an exact “unsafe after” point
- Sell-by date: mainly for store rotation, not consumer safety
So the “not an ordinary expiration date” detail you noticed is likely that Julian pack date tells the real age of the eggs, which can surprise people because eggs may be older than they seem while still being legally fine to sell.
And just to connect it to your earlier concern: even if eggs are a bit older, that doesn’t relate to the “lumps” you saw—those are still just normal internal structures like chalazae.
If you want, tell me the exact format of the date you saw (numbers/letters), and I can decode it for you.