Magic requires pixie dust. It can turn people into donkeys whenever you want on Tuesday, and nothing else. You have to decide how long the effect will last one minute before turning someone into a donkey. In order to use it, you must be the seventh son of the seventh daughter, or vice versa. You also have to be born near a toaster while your mother is riding a dog. In order for magic to work, you or the person you're casting it on have to be pregnant with quadruplets and be exactly 27 years old. You have to have had an ex- best friend named Casey, or magic won't work.
NOTE: none of these restrictions apply to the 1 millionth child of the 1 millionth child. Same with anyone who is older than their parents. If you are either of these categories you can do anything but: Summon swords, make people fart, spontaneous combust self, or turn people into donkeys. That's right, normal wizards have a leg up on you.