"The" full moon occurs at the instant the sun and the moon are in opposition (straight line with the earth in the middle viewed from far above the plane of the solar system). Ten minutes before or after it looks full, but it really isn't. The same is true twelve hours before or after. So everyone anywhere on the earth thinks they're seeing a full moon (as long as they're looking and the moon isn't obscured by clouds or other things).
ML/NJ
