Nothing magical about lactaid, it’s the pasteurizing process.
“Most” “conventional” milks do a cheaper, easier pasteurizing process that means it’ll spoil on the shelf faster. Not really a problem because that milk is usually bought quickly.
But the various milk products that sell slower, might not stay fresh on the shelf so they go above and beyond to pasteurize them to maintain a longer freshness.
In either case, those dates are for *unopened* milk. Once you open any milk you should consume it within roughly a week regardless of the date on package.
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