The International Dateline can be confusing, even
hard to rationalize in your own mind. For two descriptions, a map
and a better understanding, follow these two links.
US
Naval Observatory - History and a good map! It helps to know
where it is! A
private site by: Robert Sturgeon - If you thought it was confusing
before, try this site. The descriptions are entirely logical and
precise -- and confusing as hell.