Milk Expiry Dates

Whenever I buy a carton of milk, the first thing I do is look for an expiration date. Gotta find the milk with the farthest future date, of course. Why take home milk that's good until the 3rd when you can get some that's good until the 7th?

I do have some issues with expiry dates on milk, though. Considering that your milk comes from thousands of cows on hundreds of farms, and it all is mixed together, how exactly do they know when the milk is good until? For that matter, how do they know that anyway? Does all milk spoil at exactly the same rate? That seems unlikely to me. Also, the label says "best before" so that implies it might still be okay after the listed date.

With that in mind, here is my suggestion for a somewhat more detailed expiry date scheme for milk.