The International Date Line, which roughly follows the 180 degree meridian, lies mainly in the:

The International Date Line (IDL) is an imaginary line on the Earth's surface that roughly follows the 180 degree meridian of longitude through the middle of the Pacific Ocean. It marks the place where the calendar date changes.

How the date changes:

• When a traveller crosses the IDL going westward (from America towards Asia), the date moves forward by one day.
• When crossing eastward (from Asia towards America), the date goes back by one day.
• For example, if it is Monday just east of the line, it is Tuesday just west of it.

Why the line is needed:

• The Earth is divided into time zones, and local time changes by one hour for every 15 degrees of longitude.
• Moving east from Greenwich, time keeps going ahead; moving west, it keeps going back.

At 180 degrees, the two directions meet with a difference of a full 24 hours. The date line resolves this by marking where one calendar day ends and the next begins.

Why the line is not straight:

• The IDL zigzags to avoid splitting countries or island groups into two different dates.
• It bends east around the Chukotka region of Russia, so that all of Russia has the same date.
• It bends west around the Aleutian Islands of the USA (Alaska).
• It bends far east around Kiribati, so that all the islands of Kiribati have the same date.

Changes made by countries:

In 1995, Kiribati shifted the line so that its eastern islands, the Line Islands, moved to the western side. As a result, Kiribati became one of the first places to welcome each new day.

In 2011, Samoa moved to the west side of the line, skipping 30 December 2011, to align its date with trading partners such as Australia and New Zealand.

Why not the other options?

• ✗The 180 degree meridian does not pass through the Atlantic or Indian Oceans.
• ✗It passes through a small part of the Arctic region, but the line mainly runs through the Pacific Ocean.