Question

why is the IDL considered with respect to the 180° meridian only?

Answer 1

The 180th meridian or antimeridian[1] is themeridian 180° east or west of the Prime Meridian, with which it forms a great circledividing the earth into the Western andEastern Hemispheres. It is common to both east longitude and west longitude. It is used as the basis for the International Date Linebecause it mostly passes through the open waters of the Pacific Ocean. However, the meridian passes through Russia and Fiji as well as Antarctica.

Answer 2

1)According to the international conventions, the start of a date is considered to be at 180° meridian.

2)This is because,when one crosses the 180° meridian from east or west, there is a difference of 12 hours from prime meridian.

3)Accordingly,an adjustment or change in day time is made at 180° meridian.

Due to these reasons, the IDL is considered with respect to the 180° meridian only.