What is the purpose of the International Date Line?

The purpose of the International Date Line is to mark the boundary between two calendar days. It is located roughly along the 180-degree longitude line in the Pacific Ocean and serves as the demarcation point where the date changes. When crossing the International Date Line from west to east, one subtracts a day, and when crossing from east to west, one adds a day. This system helps to maintain a consistent and understandable calendar structure across various time zones globally.

The emphasis on calendar days is important for navigation and coordination in international travel and communication, ensuring that activities such as shipping, aviation schedules, and timekeeping are synchronized. Understanding this concept is crucial for anyone involved in navigation and international operations, as it directly impacts how time is tracked and organized on a global scale.