Explorer Benedict Allen heads to the Royal Observatory in Greenwich - 0 degrees longitude - to try to solve the riddles of the world time-zone map. Over 100 years of international political intrigue and manoeuvring have left us with an oddly jagged vast jigsaw puzzle.
In 1884 The Greenwich Meridian was agreed on as the prime meridian, centre of the world time zone map, as the globe was divided into 24 convenient, equal-size segments. Who could argue with the logic?
But it wasn't long before the map began to provide the perfect stage for international political manoeuvering and global nose-thumbing as countries divvied up the globe and chose their own time zones.
Russia opted for 11, the US eight, and to remind its subjects where the power lay, China decided to impose just one single time zone - Beijing time in the east in place of the five it should have.
India snubbed its former rulers by opting to be five and a half hours ahead of GMT. What's with the quarter-hour differences?
And what is that extraordinary dogleg on the international date line which hauls a group of South Pacific islands back from tomorrow to today?