I don’t use butter very often so it sits in my refrigerator for a while. Yesterday I wanted to use some and I looked a the “use by” date on it and it said October 2004. But it smelled and looked fine.
How long can regular sweet cream butter wrapped in sticks and contained in an opened cardboard outer box last in a refrigerator?
Should I use the butter I have? As I said, it smells and looks just dandy.
I’ve had butter sit in the butter dish for a LONG time and eventually, the color starts to turn a really bright yellow, almost orange. That’s always when I threw it out. I’m sure it was long past the use-by date. I hope somebody has an answer for this because I have some old looking butter in the fridge right now.
Depends on how cold your fridge is.
When the butter starts to smell like a dirty armpit, throw it out. Until such time, it’s fine.
I know they make a special container for butter that keeps it fresh longer. I don’t have a picture or link, but picture a small ceramic cup full of butter. attach that cup to the bottom of a jar lid. put that lid on a jar with water in it so that the water covers the lip of the cup. This keeps the butter fresh for longer periods of time than the fridge because the water seals it off from the air. And you can keep it at room temperature! Think about it fresh butter always on hand that’s alway soft and easy to work with, rather than the brick you get from the fridge. 
Eventually butter will go rancid (i.e. the fat molecules will breakdown and begin picking up some nasty tasting compounds). But since it is mostly saturated fat, that will take quite a long time. If it smells and tastes OK, then go for it. FYI, the freezer temperatures will slow the rancidity reactions even further. So, it will go even longer in the freezer.
I keep my butter at room temperature, in the cupboard, in a covered (clear plastic cover) dish.
It lasts for weeks this way, and is always easy to spread.
I’ve kept butter in the fridge for at least a year with no spoilage except some discoloration (from pale yellow to a translucent yellow) on the part exposed to the air. At room temperature, it begins to turn translucent and darker after a week or two. So I keep most of the butter in the fridge, still in the foil wrappers. It’s easier to measure with the wrapper on, and stick butter is vastly more convenient than block butter. I keep a small amount at room temperature for spreading. That way, there’s always some soft butter available for spreading, but the remainder stays fresh until it’s needed.
Then again, I might go through two pounds of butter a year, most of it for baking. A large family that uses a pound of butter a month might not need to refrigerate their butter at all.
Butter can be frozen for at least 6 months with no significant degradation in quality. If you find you don’t use butter that often, lop of a small chunk for the fridge and keep the rest in the freezer.
How about margarine and how long it will keep in the fridge?
Butter will keep for 3,000 years in an irish bog!