International Date Line
From the Simple English Wikipedia, the free encyclopedia that anyone can change
The International Date Line (IDL), also known as just the Date Line, is an imaginary line on the surface of the Earth, going from north to south in the Pacific Ocean. The date becomes one day later as one travels across it in western direction, and one day earlier as one travels across it in eastern direction.
The reason for this effect is that the countries on the eastern side of the International Date Line, (located in or outside eastern Asia) have the time zone 10-12 hours more than Greenwich. And the countries on western side of it (Alaska/Hawaii and other areas) have the time zone 9-12 hours less than Greenwich. So when travelling across the line, one's watch has to be adjusted 20-24 hours, depending on the time zones.
For example New Zealand has got the time zone Greenwich+12 hours, and Hawaii has got the time zone Greenwich-10 hours. When travelling from New Zealand to Hawaii the clocks must be switched 22 hours backwards, about one day.
