Hawaii is a group of islands in the middle of the Pacific Ocean, and thus is in the Pacific United States. It was either the 49th or 50th state of the union, depending on who you ask. It is not in the same timezone as Guam. In fact, it's not even on the same side of the international date line as Guam. Time is a funny concept.
For the record, Hawaii is in UTC−10:00 all year around.