International Date Line
The reason for this effect is that the countries on the western side of the International Date Line, (in or outside eastern Asia) have the time zone 10–12 hours more than Greenwich. And the countries on eastern 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.