The key is to keep your milk cold, and here are a few suggestions on how to do this.
Refrigerate your milk as soon as possible after purchase. For every degree above 40 that milk is exposed (including your travel time from the grocery store to your home), it loses a day of freshness.
Return your milk to the refrigerator as soon as you are finished serving or using it instead of leaving your milk on the breakfast or dinner table throughout the meal.
Check that your refrigerator temperature is set between 34 and 36 degrees.
Store your milk in the interior area of the refrigerator instead of in the door where the temperature fluctuates because of frequent opening.