The international date line is measured approximately from

The international date line is measured approximately from 180 degrees longitude.

Explanation:

Meridians and parallels are the imaginary lines used to determine degrees of latitude and geographic longitude. They differ in that the meridians are the circumferences that pass through both poles of the globe, while the parallels are the minor circles that are parallel to the equator, and which serve as the basis for determining latitude.

An antimeridian is a meridian exactly opposite to any meridian that is taken from reference, and therefore, the resulting meridian adds 180 º to that taken from reference.

The Greenwich meridian is the one from which the degrees of geographical longitude of each place on the planet are counted over the Equator. Its name is due to the fact that the imaginary line of the 0 ° meridian that passes through the two poles of the Earth crosses the English town of Greenwich.

When taking Greenwich, 0º, as its reference meridian, its antimeridian is the one located on the opposite side to 180º. This meridian is the international date change line.

So the international date change line is an imaginary surface land line drawn over the Pacific Ocean and coincident with the 180 ° meridian.

Then, the international date line is measured approximately from 180 degrees longitude.