<P> The International Date Line (IDL) is an imaginary line of demarcation on the surface of Earth that runs from the North Pole to the South Pole and demarcates the change of one calendar day to the next . It passes through the middle of the Pacific Ocean, roughly following the 180 ° line of longitude but deviating to pass around some territories and island groups . </P> <Dl> <Dd> This description is based on the most common understanding of the de facto International Date Line . See § De facto and de jure date lines below, and map above at right . </Dd> </Dl>

Where does the day start and end in the world