Regarding The Date On A Milk Carton/Bottle?

those dates are a shot in the dark and not a guarantee that it will not spoil.
A LOT depends on how it was handled before you bought it, if anyone drank out of the carton while you had it, etc.
I have had milk last weeks after the date and milk spoil BEFORE the date on it.
Thats what your nose is for.

Usually it is the sell-by date, but the date is only accurate if the product has been kept cool and handled correctly from teat to table. Easily it could have been left out of refrigeration for hours or days for a variety of reasons. From transportation issues to in store issues where it is dropped on a shelf after the customer decides against it and then placed back in the fridge case.

It's neither. It's the date by which the seller recommends that the merchant sell the product. It's called a "sell by" date.

That being said, there is no law the prohibits merchandise from being sold past the sell-by date. There is also no magical formula that guarantees which day perishable food will no longer be safe to eat. It often lasts longer than the sell-by date, occasionally it doesn't.

You did right...trust your nose.