Read the following passage and answer the question. The International Date Line (IDL) is a generally north-south imaginary line on the surface of the Earth, passing through the middle of the Pacific Ocean, which designates the place where each calendar day begins. It is roughly along 180° longitude, opposite the Prime Meridian, but it is drawn with diversions to pass around some territories and island groups. Crossing the IDL traveling has, resulted in a day, or 24 hours, being subtracted, so that the traveler repeats the date to the west of the line. Crossing west results in a day being added, that is, the date is the eastern side date plus one calendar day. The line is necessary in order to have a fixed, albeit arbitrary, boundary on the globe where the calendar date advances.

Which among the following could be the topic of the passage?

A. International Date Line
B. International Imaginary Line
C. Time Zones of the World
D. Pacific Ocean Calendar Year