When does it go bad?

So I have a container of milk from Costco in my fridge. Korean milk has a short expiration date compared to the U.S., I hear because it is not pasteurized here.
This milk passé its date on April 14, exactly one week ago. However, it tastes fine still, so I am drinking it as of yet. Any advice on this? Do the Koreans just make conservative poll-dates? I seem to remember U.S. milk going bad pretty soon after it’s poll-date, but Korean milk seems more robust. Maybe there is something to be said for massaging cows after all.