Pasteurised milk keeps about 5–7 days past the printed date when it is stored at 4 °C or below, and roughly 3 months in the freezer. The date on the carton is a quality date, not a safety cut-off.
Fridge
5–7 days after the printed date
Freezer
About 3 months (expect some separation)
Counter / pantry
Discard after 2 hours out of refrigeration
Store it right
Store on a middle shelf at the back, never in the door where temperature swings.
Keep the carton closed — milk absorbs fridge odours quickly.
Freeze in the original container with a little headspace, then thaw in the fridge.
Signs it has gone off
Sour smell
Lumps, stringiness or a yellow tint
Bloated or hissing container
Rescue ideas
Slightly soured milk still works in pancakes, scones and soda bread.