Back when the unpleasantness in Southeast Asia was going on we would occasionally sail into the Indian Ocean to rattle our sabers. Since this was beyond our logistical pipeline we would run out of stuff like milk pretty quickly. The resupply ships couldn't bring it out because it would go bad before they got to us, and there was no local source that was reliable. So we had sterilized milk. It was in four ounce cartons and was shelf-stable, no refrigeration required. Most tried it once. The taste was ghastly, to put it politely. So we did with bug juice (Kool-Aid) and water. No cereal, and it was wise to avoid anything that had to be made with milk since the taste would convey.
But yours? You might check the dairy's web site to see if they are touting a new pasteurization process. Look to see if there are other containers with similar lengthened dates. And ask the store folks if they have any idea.