International Date Line
- It is the International Date Line where the date changes by exactly one day when it is crossed. A traveller crossing the date line from east to west loses a day (because of the loss in time he has made); and while crossing the dateline from west to east he gains a day (because of the gain in time he encountered).
- A traveler going eastwards gains time from Greenwich until he reaches the meridian 180°E, when he will be 12 hours ahead of Greenwich Mean Time (GMT).
- Similarly in going westwards, he loses 12 hours when he reaches 180°W. There is thus ....