What happens when you cross the International Date Line from West to East?

When crossing the International Date Line from West to East, you subtract a day. This is due to the way that the International Date Line is designed to help maintain a standard calendar day across the globe. The line, located roughly along the 180th meridian in the Pacific Ocean, serves as a point of transition between calendar days.

When you cross from the west side of the line to the east side, you effectively move back 24 hours, meaning if it was Monday on the west side, it would become Sunday upon crossing to the east. This subtraction of a day helps to synchronize the calendar with the rotation of the Earth and the natural progression of time zones, ensuring that there is a consistent understanding of days and times worldwide.

In contrast to this, moving from east to west across the International Date Line would require you to add a day, resulting in different implications for the calendar, which is where the confusion may arise. The changes in time zones or a lack of change in the day refer to other aspects of timekeeping but don't specifically address the unique implications of crossing the Date Line itself.