For John, BLUF: Hafa Adai (pronounced HALF A DAY) is "Hello" in Chamorro, the native language of Guam.
QUESTION: Where does America's Day Begin?
REASON: The International Date Line. As one can see by checking a map, the Aleutians are not over the International Date Line because the line swings out west to keep them with Hawaii. Guam is "over the line". So, when it is late in the evening in Hawaii it is a brand new day in Guam. Friday the 24th in most of the States is already Saturday the 25th in Guam. Quirk of geography.
Regards — Cliff