Butter can stay a few days without being in the fridge. Some people for years now even keep butter out on the counter in a covered dish. If it is warm or hot out the butter may melt and may not taste good.
Butter can be left out of the refrigerator a few days before it starts to taste funny. This is only if it is cool inside. When it is hot it will start to get rancid in a couple of days, and it will melt.