Will This Milk Ever Expire ?

it means it expires 4 years after it was made

That's not how leap years work ! :~)

on leap years febuary has 29 days not 30

:~)

so yeah it never will

How does a printing robot mess up so badly to make up a day in the y-
it's either march 1st or 2nd technically.

The reason is almost certainly human error in setting the printer
Or it could be a person in the dairy having a laugh ! :~)

....maybe