If a recipe you're using calls for either cold butter or room-temperature (softened) butter specifically, there is a reason! Using butter that is at the right temperature can make all the difference in a "ho-hum" recipe and "yum" recipe.
If you need COLD butter:
Dice the butter, then freeze for 10 to 15 minutes.
If you need SOFTENED or room temperature butter:
~ And you have plenty of time, place the butter in a cool area (not near the stove or any other heat sources) and allow to sit at room temperature for several hours or overnight.
~ And you have a little time, cut the butter into small pieces and let sit at room temperature for at least 30 minutes.
~ And you have no time, microwave the butter in short 5 second intervals until pliable. Be careful not to let the butter melt.