Why is the world divided into time zones?

Answer 1

The world is divided into time zones because the sun cannot shine on the whole world at the same time. So in one part of the world it is night and the other part it is day. So time zones keep the amount of daylight and night consistent with the time across the globe.

Answer 2

Time zones were created by the railroads to make it simpler to schedule trains and print timetables.

Before time zones every town and village had its own local time determined by a sundial. This was not a problem when people rarely traveled or traveled by foot, horse, or wagons which took days to travel just a couple hundred miles. But when railroads could transport people the same distance in just a few hours it became a problem.

For example on a railroad with track running almost 1000 miles largely east-west, you cannot afford to print a different timetable for local time in each town on the route and if the people don't know when the train arrives and departs they will miss trains! By creating timezones the railroads could print a single timetable listing "railroad time" for each train in each city. Many early train stations had a large clock on the peak of their roof showing "railroad time" that was easy to see throughout the town. The official town clock often still showed local time determined by a sundial, but to avoid confusion usually eventually got reset to match the railroad's clock.

Eventually time zones became standardized worldwide (although the exact boundaries are often adjusted for convenience).