How is time adjusted when crossing the International Date Line from East to West?

When crossing the International Date Line from East to West, the correct adjustment is to add a day. This is because the International Date Line serves as a demarcation point for calendar days. When traveling in that direction, you effectively move ahead to the next calendar day.

For instance, if it is Monday when you cross the line from East to West, it becomes Tuesday after the crossing. This change reflects the fact that you have moved into a new time zone that is one day later than the one you were previously in. Each time zone generally represents a one-hour difference, but the Date Line, by its nature, creates a full day shift in the calendar.

The other choices refer to different aspects of time adjustment that don't apply in this scenario. Subtracting a day is what would occur when crossing the line from West to East. Keeping the same day would not accurately reflect the change in your calendar; the whole purpose of the International Date Line is to manage these day transitions. Changing your local clock pertains to adjusting time locally but does not address the significant shift in the day associated with crossing the Date Line. Therefore, adding a day is the appropriate action taken when crossing from East to West.