How can the International Date Line be explained in simple terms ?

The International Date Line (IDL) is an imaginary line of demarcation on the Earth's surface that separates two consecutive calendar dates [t1][t4]. In simple terms, it is located at approximately 180° longitude, which is exactly halfway around the world from the Prime Meridian (0° longitude) [c1][t1]. While the Prime Meridian passes through Greenwich, England, the IDL is situated in the mid-Pacific Ocean [c4][t2]. Crossing the line from east to west results in adding a day, while crossing from west to east results in subtracting a day [c4][t2]. Although it generally follows the 180° meridian, the line is not perfectly straight; it curves at certain points, such as the Bering Strait and various island groups like Kiribati and Tonga, to ensure that specific countries or territories remain within the same time zone and calendar day [c4][t3].

Sources

1. [1] Exploring Society:India and Beyond. Social Science-Class VI . NCERT(Revised ed 2025) > Chapter 1: Locating Places on the Earth > Before we move on ... > p. 24
2. [2] Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 2: The Earth's Crust > The International Date Line > p. 14
3. [3] https://oceanservice.noaa.gov/facts/international-date-line.html