Originally Posted by Shell_of_the_South
The Wizarding World of Harry Potter is one section of the Islands of Adventure theme park. HP would not take a full day, but the entire park would probably take a full day if you want to do everything. Universal Studios is a separate park. If you want to visit both theme parks you would need the park to park ticket. I personally wouldn't try to do both parks in one day, especially the week after Christmas.
Perfect! That's just what I needed to know.