A day in DnD can last for as long or as short (in terms of actual time passed) as the DM wants it to. an in-game day can also last for as long or as short of a time as the DM wants it to be. the...
For any sacrificing you'll need a Temple, at least 3*3 square big. Pick up the creature you want to sacrifice, and drop it into the central pool of your Temple.