The precise measurement is 365.2425 days per year. Every four years is a leap year except every hundredth year (turn of the century), except every four hundred years which is a leap year again (which is why 2000 was a leap year). But even this isn't 100% accurate which is why we now have leap seconds every once in a while. Of course the speed at which the planet revolves around the Sun is constantly changing depending on all kinds of things, making the whole thing a bit ridiculous.
