What is the purpose of the International Date Line?

The purpose of the International Date Line is to indicate the start of each new day. It serves as an imaginary line located primarily along the 180-degree meridian in the Pacific Ocean, where the date changes. When crossing the International Date Line from west to east, one subtracts a day, while crossing from east to west, one adds a day. This mechanism helps maintain a consistent timekeeping system across different regions of the world, ensuring that as one travels east or west, they know when a new day begins.

The other options do not accurately reflect the purpose of the International Date Line; for instance, it does not divide time zones equally or serve as a boundary for international waters. Additionally, it is unrelated to the equator, which marks the division between the Northern and Southern Hemispheres.