Where does the international dateline start?

Answer 1

The International Dateline starts and ends at the poles (North Pole and South Pole). The International Date Line (IDL) is an imaginary line on the surface of the Earth opposite the Prime Meridian where the date changes as one travels east or west across it. Roughly along 180° longitude, with diversions to pass around some territories and island groups, it mostly corresponds to the time zone boundary separating +12 and −12 hours Coordinated Universal Time (UTC) (Greenwich Mean Time -- GMT). Crossing the IDL travelling east results in a day or approximately 24 hours being subtracted, and crossing west results in a day being added. The exact number of hours depends on the time zones.