It's my understanding that the 7-night Disney Magic Cruise is primarily on Atlantic Standard Time, which is Eastern Standard Time plus 1 hour, or Central Standard Time plus two hours, or Greenwich Mean Time minus 4 hours. That's because the ship is sailing in the Atlantic time zone, which includes St. Maarten and St. Thomas.
The islands do not change to Daylight Saving Time, so passengers who sail during Eastern Daylight Time (late spring, summer, and early fall) don't experience any time change. (Eastern Daylight Time and Atlantic Standard Time are both Greenwich Mean Time minus 4 hours.)
But this time of year, there will a one hour time change on Sunday night.
That's one reason we chose late seating for dinner. We're from the Central time zone. So 6:00 p.m. and 8:15 p.m. AST dinner seating will feel like 4:00 p.m. and 6:15 p.m. CST. 4:00 p.m. is way too early for dinner.