1 To freeze butter, wrap tightly in heavy-duty aluminum foil or plastic freezer wrap, or place inside a heavy-duty freezer bag.  Frozen salted butter will generally keep longer (up to 9 months for best quality) than unsalted butter (5-6 months for best quality).
http://stilltasty.com/fooditems/index/16649
FOOD STORAGE — HOW LONG CAN YOU KEEP... BUTTER — UNOPENED OR OPENED PACKAGE. 1  Butter that has been continuously refrigerated will usually keep for about one month after the sell by date on the package.  If butter develops an off odor, flavor or appearance, it should be discarded.
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Milk, cream, and yogurt are all stored in the refrigerator without question. Left at room temperature, it doesn't take long before they start to spoil. Butter is, after all, made from cream, so there is logic in thinking that it, like cream, should also be stored in the fridge — but there's a difference. The primary component of butter is fat (at least 80 percent).
http://www.thekitchn.com/does-butter-really-need-to-be-refrigerated-224036
1 Butter may be left at room temperature for 1-2 days, but it will begin to spoil rapidly if not refrigerated after that.  Do not store butter in the molded butter compartment of the refrigerator door for more than one week — butter will keep much longer when stored in the main body of the refrigerator.
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Tips for Leaving Butter at Room Temperature. For long-term storage, it is still safest to store butter wrapped or covered in the refrigerator. But for spreadable butter bliss, a small amount can be stored, fully covered, at room temperature — with a few caveats.
http://www.thekitchn.com/does-butter-really-need-to-be-refrigerated-224036
1 Butter that has been continuously refrigerated will usually keep for about one month after the sell by date on the package.  If butter develops an off odor, flavor or appearance, it should be discarded.
http://stilltasty.com/fooditems/index/16649
Overnight, the butter would spoil, yes, You can smell spoiled butter (I made a piecrust once but didn't use it, yet it spoiled even though it was in the fridge), and from morning to night, sure it would spoil.
http://www.care2.com/greenliving/butter-in-the-fridge-or-safe-to-leave-on-the-counter.html
Carol Cox4 years ago. i keep mine in the freezer and take out what we need. usually a stick a day if I am not baking something...we leave the stick of butter out all day, in a butter dish..it rarely lasts very long. butter is better for you than margarine.
http://www.care2.com/greenliving/butter-in-the-fridge-or-safe-to-leave-on-the-counter.html
1 Do not store butter in the molded butter compartment of the refrigerator door for more than one week — butter will keep much longer when stored in the main body of the refrigerator.  To freeze butter, wrap tightly in heavy-duty aluminum foil or plastic freezer wrap, or place inside a heavy-duty freezer bag.
http://stilltasty.com/fooditems/index/16649
The USDA guidelines state that butter should be stored in its original protective wrapping or a “container until ready for use,” and to remove from the refrigerator 10 to 15 minutes before use. The USDA even goes one step further and suggests freezing butter not intended for use within two or three days.
http://www.care2.com/greenliving/butter-in-the-fridge-or-safe-to-leave-on-the-counter.html
how long can i keep butter in the refrigerator
Butter that has been continuously refrigerated will usually keep for about one month after the sell by date on the package.