The International Date Line must therefore be observed in conjunction with Earth's time zones: the net adjustment to one's watch is zero. If one crosses the date line at precisely midnight, going westward, one skips an entire day; while going eastward, one repeats the entire day. Learn what the International Date Line is, where it is located and how it affects the calendar days. Find out which countries are close to the line and which one starts the day first. The International Date Line (IDL) is an imaginary line on the Earth’s surface that primarily runs along the 180° longitude, separating two consecutive calendar dates. It is not a straight line but zigzags to avoid splitting countries into different days. The line plays a crucial role in global timekeeping and navigation, ensuring the continuity of the 24-hour time system across the world. International Date Line, imaginary line extending between the North Pole and the South Pole and arbitrarily demarcating each calendar day from the next.
