Butter should be stored at a low temperature, in a cool dark place. For best results butter should be stored in the refrigerator. Butter should be kept wrapped in its original wrapper, plastic wrap or in a covered butter dish. It is important to wrap butter well before refrigerating it to prevent it from absorbing other odours in the refrigerator.
The expiration date is written on the wrapping of the butter. To give you an idea how long butter can be stored the following rules of thumb can be used:
Unopened and unsalted butter can be refrigerated for 8 weeks. Salted butter in its original packaging can be refrigerated for 12 weeks. Once a pack of butter is opened, it should be used within 3 weeks. Butter can also be frozen for about 6 months. After freezing, butter has a tendency to taste saltier.