The time change on the western will vary depending on whether you sail during Daylight Saving Time or not. During standard time, the ship's clock will be set back an hour between Grand Cayman and Cozumel (Grand Cayman is roughly due south of the southern tip of Florida and is in the Eastern time zone). During DST, the clock is set back between Key West and Grand Cayman, as Grand Cayman does not observe DST. Either way, the clock will be set forward again between Cozumel and Castaway Cay.
On the Eastern, the clock is set forward an hour on Sunday night, and set back an hour on Thursday night if you sail during Standard time. During DST, the clock is not changed, because neither St. Thomas nor St. Maarten observe DST, so while they are on Atlantic Standard Time, it ends up being the same as EDT.
On a general note, I believe DST begins this Sunday in the US.
Yes. By that time, the ship's clock will be set at island time. The time changes during the cruise ensure that ship time and port time will always be the same.
Make sure to change your watch to the current ships time (which is island time) whenever you are told to change times (there will be a notice in your room the evening before the change occurs). This way you will not inadvertently be late back to the ship (more of a problem on the eastern cruise).
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