Very true. Sometimes milk will start to go before its 'use by' date and sometimes it can be as sweet as the day it was opened two+ weeks after.
When I'm in doubt I pour a little in a glass and taste just a touch of it. No need to take a swallow to know if it's good or bad.
I drink raw milk so I am super careful.
The taste is far better than pasteurized, but it’s never more than 24 hrs from the cow with very low somatic cell count.
Milk can spoil earlier than posted if your refrigerator door is being opened and closed regularly people with teenagers would have this problem, when I was a teenager I used to stand with the frig door open just looking!!!