  == Leap Year == Yes, the terms can be grouped either way, but there's one way that's more efficient and also demonstrates that only years that are multiples of 4 are potentially leap years.  And leaving the parens out will, in most programming languages, group them the other way (and being higher precedence than or).  So I don't really see the point of your edit, but since I don't want to prolong an edit war, I leave it to you to do something about (or not).   