Final answer:
The International Date Line is an imaginary boundary located mainly at the 180° longitude meridian in the Pacific Ocean, where the date changes by one day when it is crossed. It ensures consistent timekeeping as people travel around the globe.
Step-by-step explanation:
The International Date Line is an arbitrary line near the 180° longitude meridian, running mainly through the Pacific Ocean. It is the line that separates two consecutive calendar days. As you travel around the Earth and cross different time zones, there’s a need for a consistent point to change the date. When you cross the International Date Line from east to west, you add a day, and when you cross from west to east, you subtract a day.
This avoids confusion that would arise if every point on Earth could decide its own date. It's important not to confuse the International Date Line with time zones, or with the prime meridian (0 longitude) which sets time zones. The line is drawn with some deviations to accommodate international border agreements and to prevent the line from cutting through islands or countries, such as Alaska.
In summary, the International Date Line acts as the demarcation line that shifts the calendar date by a whole day. It is the answer to ensuring that as we move across the planet, time is kept consistently. Hence, the correct description for the International Date Line would be: 1) A line that separates two consecutive calendar days.