- The International Date Line is an imaginary line on Earth's surface defining the boundary between one day and the next. - It lies roughly halfway around the world from the prime meridian (0° longitude), at about 180° longitude. - It crosses mainly over the Pacific Ocean, deviating (zigzagging) around landmasses such as the Bering Strait, the Aleutian Islands, and island nations like Kiribati, Samoa, and Fiji to avoid splitting them into different calendar days. - Therefore, the International Date Line crosses over the Pacific Ocean.