Why is the International Date Line so winding? Going around Kiribati

Kiribati is located in the central Pacific Ocean and consists of 33 islands of various sizes (21 of which have permanent residents).

Kiribati has a land area of ​​about 811 square kilometers, which is about 2/3 of Chongming Island. Kiribati is not large in area and is divided into three major archipelagos: Gilbert, Phoenix and Line. The islands are far apart, spanning more than 3,800 kilometers from east to west, and its exclusive economic zone covers an area of ​​3.5 million square kilometers.

Kiribati has a population of about 116,000, of which more than 90% are Micronesians. It was once a British colony and its official language is English. Tarawa, the capital of Kiribati, is located in the southern part of Tarawa Atoll in the Gilbert Islands and has a population of about 50,000.

Kiribati is the only country in the world that spans both the northern and southern hemispheres and the eastern and western hemispheres, and the International Date Line runs around it.

Before the Age of Exploration, most people believed that the world was flat, with the east and west ends far apart. During the Age of Exploration, Magellan believed that the earth was round, and decided to sail around the world to prove that the earth was indeed round.

In 1519, with the help of the King of Spain, Magellan formed a fleet and left Spain with hundreds of people, sailing towards the vast Atlantic Ocean.

Magellan's fleet sailed southwest to South America, then sailed south along the east coast of South America, and entered the Pacific Ocean through Tierra del Fuego, the southernmost island of South America. The strait between the South American continent and Tierra del Fuego was later named the Strait of Magellan. After that, the fleet crossed the entire Pacific Ocean and entered the Philippine Islands in Southeast Asia. Unfortunately, Magellan himself died there. A few years later, the fleet returned to Spain via the Indian Ocean and the Cape of Good Hope in southern Africa. It turns out that the earth is indeed round.

The surviving crew members discovered that the logbook they recorded was one day shorter than the date on land. This caused a sensation at the time, and some even suspected that the sun had eaten one day of human life.

Later people discovered the secret: if a fleet sailed around the earth from east to west, it would take one day less, while if it sailed around the earth from west to east, it would take one day more.

As people continue to discover the earth, they need to determine the position and direction of the earth so that people can locate themselves during long-distance voyages. There is a north-south line at the original site of the Greenwich Observatory in London, the capital of the United Kingdom, which is designated as the 0° longitude (or prime meridian). Correspondingly, on the other side of the earth, there should be a line where the 180° east longitude and the 180° west longitude coincide.

In order to solve the problem of one more or less day on a route around the earth, the line where the 180° east longitude and the 180° west longitude coincide is designated as the International Date Line.

The 180° east longitude line passes through the Chukotka Peninsula. In order to make Asia and North America different in date, the International Date Line bypasses the Chukotka Peninsula and goes south through the Bering Strait. Since the long and narrow Aleutian Islands in southwestern Alaska also span the eastern and western hemispheres, the International Date Line bypasses the Aleutian Islands and then returns to the 180° east longitude line (180° west longitude line).

The 180° east longitude line goes south to the equator. Although it does not pass directly through any island, it passes through Kiribati, which is 3,800 kilometers away from east to west. In order to keep Kiribati on the same day, the International Date Line bypasses it from the east.

By the same token, the International Date Line goes south, bypassing the island nations of Tuvalu and Fiji, and then turns back to coincide with the 180° east longitude to the southeast of New Zealand.

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